Split tab-layout into `template` & `tabs` section

* adjust example layouts and move them from `./example` to
  `./example/layouts`

* simplify the deserialization of the layout

* layouts are now constructed as follows:

```
---
template:
  direction: Horizontal
  parts:
    - direction: Vertical
      borderless: true
      split_size:
        Fixed: 1
      run:
        plugin: tab-bar
    - direction: Vertical
      body: true # <== The body section specifies the position of the
      # inserted tab
    - direction: Vertical
      borderless: true
      split_size:
        Fixed: 2
      run:
        plugin: status-bar
tabs:
  - direction: Vertical
  - direction: Vertical
```

19 files changed, 507 insertions, 613 deletions

diff --git a/example/layouts/multiple_tabs_layout.yaml b/example/layouts/multiple_tabs_layout.yaml
new file mode 100644
index 000000000..cba76b88d
--- /dev/null
+++ b/example/layouts/multiple_tabs_layout.yaml
@@ -0,0 +1,87 @@
+---
+template:
+  direction: Horizontal
+  parts:
+    - direction: Vertical
+      split_size:
+        Fixed: 1
+      run:
+        plugin: tab-bar
+      borderless: true
+    - direction: Vertical
+      body: true
+    - direction: Vertical
+      split_size:
+        Fixed: 2
+      run:
+        plugin: status-bar
+      borderless: true
+
+tabs:
+- direction: Vertical
+  parts:
+  - direction: Vertical
+    split_size:
+      Percent: 50
+  - direction: Vertical
+    split_size:
+      Percent: 50
+- direction: Vertical
+- direction: Vertical
+  parts:
+    - direction: Vertical
+      split_size:
+        Percent: 50
+    - direction: Vertical
+      split_size:
+        Percent: 50
+- direction: Vertical
+  parts:
+  - direction: Vertical
+    split_size:
+      Percent: 50
+  - direction: Horizontal
+    split_size:
+      Percent: 50
+    parts:
+      - direction: Vertical
+        split_size:
+          Percent: 50
+      - direction: Vertical
+        split_size:
+          Percent: 50
+- direction: Vertical
+- direction: Vertical
+- direction: Vertical
+- direction: Vertical
+  parts:
+  - direction: Vertical
+    split_size:
+      Percent: 20
+    run:
+      plugin: strider
+  - direction: Horizontal
+    split_size:
+      Percent: 80
+    parts:
+      - direction: Vertical
+        split_size:
+          Percent: 50
+      - direction: Vertical
+        split_size:
+          Percent: 50
+- direction: Vertical
+  parts:
+  - direction: Vertical
+    split_size:
+      Percent: 40
+  - direction: Horizontal
+    split_size:
+      Percent: 60
+    parts:
+      - direction: Vertical
+        split_size:
+          Percent: 50
+      - direction: Vertical
+        split_size:
+          Percent: 50
diff --git a/example/layouts/multiple_tabs_layout_htop_command.yaml b/example/layouts/multiple_tabs_layout_htop_command.yaml
new file mode 100644
index 000000000..13901c130
--- /dev/null
+++ b/example/layouts/multiple_tabs_layout_htop_command.yaml
@@ -0,0 +1,90 @@
+---
+template:
+  direction: Horizontal
+  parts:
+    - direction: Vertical
+      split_size:
+        Fixed: 1
+      run:
+        plugin: tab-bar
+      borderless: true
+    - direction: Vertical
+      body: true
+    - direction: Vertical
+      split_size:
+        Fixed: 2
+      run:
+        plugin: status-bar
+      borderless: true
+
+tabs:
+- direction: Vertical
+  parts:
+  - direction: Vertical
+    split_size:
+      Percent: 50
+    run:
+      command: {cmd: htop}
+  - direction: Vertical
+    split_size:
+      Percent: 50
+- direction: Vertical
+  parts:
+    - direction: Vertical
+      split_size:
+        Percent: 50
+    - direction: Vertical
+      split_size:
+        Percent: 50
+- direction: Vertical
+  parts:
+  - direction: Vertical
+    split_size:
+      Percent: 50
+  - direction: Horizontal
+    split_size:
+      Percent: 50
+    parts:
+      - direction: Vertical
+        split_size:
+          Percent: 50
+      - direction: Vertical
+        split_size:
+          Percent: 50
+- direction: Vertical
+- direction: Vertical
+  run:
+    command: {cmd: htop, args: ["-C"]}
+- direction: Vertical
+- direction: Vertical
+  parts:
+  - direction: Vertical
+    split_size:
+      Percent: 20
+    run:
+      plugin: strider
+  - direction: Horizontal
+    split_size:
+      Percent: 80
+    parts:
+      - direction: Vertical
+        split_size:
+          Percent: 50
+      - direction: Vertical
+        split_size:
+          Percent: 50
+- direction: Vertical
+  parts:
+  - direction: Vertical
+    split_size:
+      Percent: 40
+  - direction: Horizontal
+    split_size:
+      Percent: 60
+    parts:
+      - direction: Vertical
+        split_size:
+          Percent: 50
+      - direction: Vertical
+        split_size:
+          Percent: 50
diff --git a/example/layouts/run_htop_layout.yaml b/example/layouts/run_htop_layout.yaml
new file mode 100644
index 000000000..91f4f63cb
--- /dev/null
+++ b/example/layouts/run_htop_layout.yaml
@@ -0,0 +1,21 @@
+---
+tabs:
+  - direction: Vertical
+    parts:
+      - direction: Horizontal
+        split_size:
+          Percent: 50
+        parts:
+          - direction: Vertical
+            split_size:
+              Percent: 50
+          - direction: Vertical
+            split_size:
+              Percent: 50
+            run:
+              command: {cmd: htop}
+      - direction: Horizontal
+        split_size:
+          Percent: 50
+        run:
+          command: {cmd: htop}
diff --git a/example/layouts/run_htop_layout_with_plugins.yaml b/example/layouts/run_htop_layout_with_plugins.yaml
new file mode 100644
index 000000000..2868cba52
--- /dev/null
+++ b/example/layouts/run_htop_layout_with_plugins.yaml
@@ -0,0 +1,33 @@
+---
+tabs:
+  - direction: Horizontal
+    parts:
+      - direction: Vertical
+        split_size:
+          Fixed: 1
+        run:
+          plugin: tab-bar
+        borderless: true
+      - direction: Vertical
+        parts:
+        - direction: Vertical
+          parts:
+          - direction: Vertical
+            split_size:
+              Percent: 50
+            run:
+              command: {cmd: htop}
+          - direction: Vertical
+            split_size:
+              Percent: 50
+            run:
+              command: {cmd: htop, args: ["-C"]}
+      - direction: Vertical
+        split_size:
+          Fixed: 5
+      - direction: Vertical
+        split_size:
+          Fixed: 2
+        run:
+          plugin: status-bar
+        borderless: true
diff --git a/example/multiple_tabs_layout.yaml b/example/multiple_tabs_layout.yaml
deleted file mode 100644
index 6c4d15980..000000000
--- a/example/multiple_tabs_layout.yaml
+++ /dev/null
@@ -1,82 +0,0 @@
----
-direction: Horizontal
-parts:
-  - direction: Vertical
-    split_size:
-      Fixed: 1
-    run:
-      plugin: tab-bar
-  - direction: Vertical
-    tabs:
-    - direction: Vertical
-      parts:
-      - direction: Vertical
-        split_size:
-          Percent: 50
-      - direction: Vertical
-        split_size:
-          Percent: 50
-    - direction: Vertical
-    - direction: Vertical
-      parts:
-        - direction: Vertical
-          split_size:
-            Percent: 50
-        - direction: Vertical
-          split_size:
-            Percent: 50
-    - direction: Vertical
-      parts:
-      - direction: Vertical
-        split_size:
-          Percent: 50
-      - direction: Horizontal
-        split_size:
-          Percent: 50
-        parts:
-          - direction: Vertical
-            split_size:
-              Percent: 50
-          - direction: Vertical
-            split_size:
-              Percent: 50
-    - direction: Vertical
-    - direction: Vertical
-    - direction: Vertical
-    - direction: Vertical
-      parts:
-      - direction: Vertical
-        split_size:
-          Percent: 20
-        run:
-          plugin: strider
-      - direction: Horizontal
-        split_size:
-          Percent: 80
-        parts:
-          - direction: Vertical
-            split_size:
-              Percent: 50
-          - direction: Vertical
-            split_size:
-              Percent: 50
-    - direction: Vertical
-      parts:
-      - direction: Vertical
-        split_size:
-          Percent: 40
-      - direction: Horizontal
-        split_size:
-          Percent: 60
-        parts:
-          - direction: Vertical
-            split_size:
-              Percent: 50
-          - direction: Vertical
-            split_size:
-              Percent: 50
-  - direction: Vertical
-    split_size:
-      Fixed: 2
-    run:
-      plugin: status-bar
diff --git a/example/multiple_tabs_layout_htop_command.yaml b/example/multiple_tabs_layout_htop_command.yaml
deleted file mode 100644
index 6739eba8f..000000000
--- a/example/multiple_tabs_layout_htop_command.yaml
+++ /dev/null
@@ -1,85 +0,0 @@
----
-direction: Horizontal
-parts:
-  - direction: Vertical
-    split_size:
-      Fixed: 1
-    run:
-      plugin: tab-bar
-  - direction: Vertical
-    tabs:
-    - direction: Vertical
-      parts:
-      - direction: Vertical
-        split_size:
-          Percent: 50
-        run:
-          command: {cmd: htop}
-      - direction: Vertical
-        split_size:
-          Percent: 50
-    - direction: Vertical
-      parts:
-        - direction: Vertical
-          split_size:
-            Percent: 50
-        - direction: Vertical
-          split_size:
-            Percent: 50
-    - direction: Vertical
-      parts:
-      - direction: Vertical
-        split_size:
-          Percent: 50
-      - direction: Horizontal
-        split_size:
-          Percent: 50
-        parts:
-          - direction: Vertical
-            split_size:
-              Percent: 50
-          - direction: Vertical
-            split_size:
-              Percent: 50
-    - direction: Vertical
-    - direction: Vertical
-      run:
-        command: {cmd: htop, args: ["-C"]}
-    - direction: Vertical
-    - direction: Vertical
-      parts:
-      - direction: Vertical
-        split_size:
-          Percent: 20
-        run:
-          plugin: strider
-      - direction: Horizontal
-        split_size:
-          Percent: 80
-        parts:
-          - direction: Vertical
-            split_size:
-              Percent: 50
-          - direction: Vertical
-            split_size:
-              Percent: 50
-    - direction: Vertical
-      parts:
-      - direction: Vertical
-        split_size:
-          Percent: 40
-      - direction: Horizontal
-        split_size:
-          Percent: 60
-        parts:
-          - direction: Vertical
-            split_size:
-              Percent: 50
-          - direction: Vertical
-            split_size:
-              Percent: 50
-  - direction: Vertical
-    split_size:
-      Fixed: 2
-    run:
-      plugin: status-bar
diff --git a/example/run_htop_layout.yaml b/example/run_htop_layout.yaml
deleted file mode 100644
index 949435d69..000000000
--- a/example/run_htop_layout.yaml
+++ /dev/null
@@ -1,20 +0,0 @@
----
-direction: Vertical
-parts:
-  - direction: Horizontal
-    split_size:
-      Percent: 50
-    parts:
-      - direction: Vertical
-        split_size:
-          Percent: 50
-      - direction: Vertical
-        split_size:
-          Percent: 50
-        run:
-          command: {cmd: htop}
-  - direction: Horizontal
-    split_size:
-      Percent: 50
-    run:
-      command: {cmd: htop}
diff --git a/example/run_htop_layout_with_plugins.yaml b/example/run_htop_layout_with_plugins.yaml
deleted file mode 100644
index 99f72edbe..000000000
--- a/example/run_htop_layout_with_plugins.yaml
+++ /dev/null
@@ -1,30 +0,0 @@
----
-direction: Horizontal
-parts:
-  - direction: Vertical
-    split_size:
-      Fixed: 1
-    run:
-      plugin: tab-bar
-  - direction: Vertical
-    parts:
-    - direction: Vertical
-      parts:
-      - direction: Vertical
-        split_size:
-          Percent: 50
-        run:
-          command: {cmd: htop}
-      - direction: Vertical
-        split_size:
-          Percent: 50
-        run:
-          command: {cmd: htop, args: ["-C"]}
-  - direction: Vertical
-    split_size:
-      Fixed: 5
-  - direction: Vertical
-    split_size:
-      Fixed: 2
-    run:
-      plugin: status-bar
diff --git a/nonexistent.yaml b/nonexistent.yaml
new file mode 100644
index 000000000..740bde92a
--- /dev/null
+++ b/nonexistent.yaml
@@ -0,0 +1,2 @@
+---
+borderless: false
diff --git a/zellij-client/src/lib.rs b/zellij-client/src/lib.rs
index f74a74ddf..e806ec3bf 100644
--- a/zellij-client/src/lib.rs
+++ b/zellij-client/src/lib.rs
@@ -14,14 +14,14 @@ use crate::{
     command_is_executing::CommandIsExecuting, input_handler::input_loop,
     os_input_output::ClientOsApi,
 };
-use zellij_utils::cli::CliArgs;
 use zellij_utils::{
     channels::{self, ChannelWithContext, SenderWithContext},
     consts::{SESSION_NAME, ZELLIJ_IPC_PIPE},
     errors::{ClientContext, ContextType, ErrorInstruction},
-    input::{actions::Action, config::Config, layout::LayoutTemplate, options::Options},
+    input::{actions::Action, config::Config, options::Options},
     ipc::{ClientAttributes, ClientToServerMsg, ExitReason, ServerToClientMsg},
 };
+use zellij_utils::{cli::CliArgs, input::layout::LayoutFromYaml};
 
 /// Instructions related to the client-side application
 #[derive(Debug, Clone)]
@@ -87,7 +87,7 @@ pub fn start_client(
     opts: CliArgs,
     config: Config,
     info: ClientInfo,
-    layout: Option<LayoutTemplate>,
+    layout: Option<LayoutFromYaml>,
 ) {
     info!("Starting Zellij client!");
     let clear_client_terminal_attributes = "\u{1b}[?1l\u{1b}=\u{1b}[r\u{1b}12l\u{1b}[?1000l\u{1b}[?1002l\u{1b}[?1003l\u{1b}[?1005l\u{1b}[?1006l\u{1b}[?12l";
diff --git a/zellij-server/src/lib.rs b/zellij-server/src/lib.rs
index d0b3b5d27..e9848e702 100644
--- a/zellij-server/src/lib.rs
+++ b/zellij-server/src/lib.rs
@@ -36,7 +36,7 @@ use zellij_utils::{
     input::{
         command::{RunCommand, TerminalAction},
         get_mode_info,
-        layout::LayoutTemplate,
+        layout::LayoutFromYaml,
         options::Options,
     },
     ipc::{ClientAttributes, ClientToServerMsg, ExitReason, ServerToClientMsg},
@@ -50,7 +50,7 @@ pub(crate) enum ServerInstruction {
         ClientAttributes,
         Box<CliArgs>,
         Box<Options>,
-        Option<LayoutTemplate>,
+        Option<LayoutFromYaml>,
     ),
     Render(Option<String>),
     UnblockInputThread,
@@ -245,9 +245,6 @@ pub fn start_server(os_input: Box<dyn ServerOsApi>, socket_path: PathBuf) {
                         if !&layout.tabs.is_empty() {
                             for tab_layout in layout.tabs {
                                 spawn_tabs(Some(tab_layout.clone()));
-                                // Spawning tabs in too quick succession might mess up the layout
-                                // TODO: investigate why
-                                thread::sleep(std::time::Duration::from_millis(250));
                             }
                         } else {
                             spawn_tabs(None);
@@ -329,7 +326,7 @@ fn init_session(
     to_server: SenderWithContext<ServerInstruction>,
     client_attributes: ClientAttributes,
     session_state: Arc<RwLock<SessionState>>,
-    layout: Option<LayoutTemplate>,
+    layout: Option<LayoutFromYaml>,
 ) -> SessionMetaData {
     let (to_screen, screen_receiver): ChannelWithContext<ScreenInstruction> = channels::unbounded();
     let to_screen = SenderWithContext::new(to_screen);
diff --git a/zellij-server/src/pty.rs b/zellij-server/src/pty.rs
index 5c0e4a269..011b45cab 100644
--- a/zellij-server/src/pty.rs
+++ b/zellij-server/src/pty.rs
@@ -20,7 +20,7 @@ use zellij_utils::{
     errors::{get_current_ctx, ContextType, PtyContext},
     input::{
         command::TerminalAction,
-        layout::{Layout, LayoutTemplate, Run, TabLayout},
+        layout::{Layout, LayoutFromYaml, Run, TabLayout},
     },
     logging::debug_to_file,
 };
@@ -60,7 +60,7 @@ pub(crate) struct Pty {
     task_handles: HashMap<RawFd, JoinHandle<()>>,
 }
 
-pub(crate) fn pty_thread_main(mut pty: Pty, maybe_layout: Option<LayoutTemplate>) {
+pub(crate) fn pty_thread_main(mut pty: Pty, maybe_layout: Option<LayoutFromYaml>) {
     loop {
         let (event, mut err_ctx) = pty.bus.recv().expect("failed to receive event on channel");
         err_ctx.add_call(ContextType::Pty((&event).into()));
@@ -88,8 +88,8 @@ pub(crate) fn pty_thread_main(mut pty: Pty, maybe_layout: Option<LayoutTemplate>
             }
             PtyInstruction::NewTab(terminal_action, tab_layout) => {
                 if let Some(layout) = maybe_layout.clone() {
-                    let merged_layout = layout.construct_tab_layout(tab_layout);
-                    pty.spawn_terminals_for_layout(merged_layout, terminal_action.clone());
+                    let merged_layout = layout.template.insert_tab_layout(tab_layout);
+                    pty.spawn_terminals_for_layout(merged_layout.into(), terminal_action.clone());
                 } else {
                     let pid = pty.spawn_terminal(terminal_action.clone());
                     pty.bus
diff --git a/zellij-utils/src/input/layout.rs b/zellij-utils/src/input/layout.rs
index 15c964fe2..a3da6abab 100644
--- a/zellij-utils/src/input/layout.rs
+++ b/zellij-utils/src/input/layout.rs
@@ -20,8 +20,6 @@ use std::path::{Path, PathBuf};
 use std::vec::Vec;
 use std::{fs::File, io::prelude::*};
 
-use super::config::{LayoutMissingTabSectionError, LayoutPartAndTabError};
-
 #[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq)]
 #[serde(crate = "self::serde")]
 pub enum Direction {
@@ -52,8 +50,6 @@ pub struct Layout {
     pub direction: Direction,
     #[serde(default)]
     pub parts: Vec<Layout>,
-    #[serde(default)]
-    pub tabs: Vec<TabLayout>,
     pub split_size: Option<SplitSize>,
     pub run: Option<Run>,
     #[serde(default)]
@@ -64,9 +60,10 @@ pub struct Layout {
 // a yaml configuration file
 #[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq)]
 #[serde(crate = "self::serde")]
+#[serde(default)]
 pub struct LayoutFromYaml {
-    //#[serde(default)]
-    pub template: LayoutTemplateFromYaml,
+    #[serde(default)]
+    pub template: LayoutTemplate,
     #[serde(default)]
     pub borderless: bool,
     #[serde(default)]
@@ -84,6 +81,7 @@ impl LayoutFromYaml {
         let mut layout = String::new();
         layout_file.read_to_string(&mut layout)?;
         let layout: LayoutFromYaml = serde_yaml::from_str(&layout)?;
+
         Ok(layout)
     }
 
@@ -112,16 +110,6 @@ impl LayoutFromYaml {
                 ))
             })
     }
-
-    pub fn construct_layout_template(&self) -> LayoutTemplate {
-        let (pre_tab, post_tab) = self.template.split_template().unwrap();
-        LayoutTemplate {
-            pre_tab: pre_tab.into(),
-            post_tab: Layout::from_vec_template_layout(post_tab),
-            tabs: self.tabs.clone(),
-        }
-    }
-
     // Currently still needed but on nightly
     // this is already possible:
     // HashMap<&'static str, Vec<u8>>
@@ -162,58 +150,43 @@ impl LayoutFromYaml {
 // construct the layout
 #[derive(Debug, Serialize, Deserialize, Clone, PartialEq, Eq)]
 #[serde(crate = "self::serde")]
-pub struct LayoutTemplateFromYaml {
+pub struct LayoutTemplate {
     pub direction: Direction,
     #[serde(default)]
     pub