Add `tabs` to `layouts`

fixes #603, fixes #349

* The layout has now a unique `tabs` section,
  that can be used, like the `parts` section,
  everything that is not inside the tabs section
  is assumed to be present on every single tab
  that is opened.

  This is a BREAKING CHANGE for people that use
  custom `layouts` already, since the `tabs` section
  is not optional - for clarity and intentionality reasons.

  The functionality to specify multiple tabs is already there,
  but is still gated behind a panic, until #621 is fixed.
  So for now one tab can be specified to load on startup.

* The `NewTab` action can optionally be bound to open
  a layout that is assumed to be in the new `tabs` section

  This is a BREAKING CHANGE for people that have the
  `NewTab` action already bound in the config file:

```
- action: [NewTab, ]
  key: [F: 5,]
```
must now be specified as:
```
- action: [NewTab: ,]
  key: [F: 5,]
```
  Optionally a layout that should be opened on the new tab can be
  specified:
```
- action: [NewTab: {
  direction: Vertical,
  parts: [ {direction: Horizontal, split_size: {Percent: 50}}, {direction: Horizontal, run: {command: {cmd: "htop"}}},],
  key: [F: 6,]
```
or:
```
- action: [NewTab: {direction: Vertical, run: {command: {cmd: "htop"} }},]
  key: [F: 7,]
```
or
```
- action: [NewTab: {
  direction: Vertical,
  parts: [ {direction: Vertical, split_size: {Percent: 25},run: {plugin: "strider" }}, {direction: Horizontal}],}, MoveFocus: Left,]
  key: [F: 8,]

```

2 files changed, 3 insertions, 3 deletions

diff --git a/zellij-client/src/input_handler.rs b/zellij-client/src/input_handler.rs
index f02b5ad81..19b0f6291 100644
--- a/zellij-client/src/input_handler.rs
+++ b/zellij-client/src/input_handler.rs
@@ -183,7 +183,7 @@ impl InputHandler {
             }
             Action::CloseFocus
             | Action::NewPane(_)
-            | Action::NewTab
+            | Action::NewTab(_)
             | Action::GoToNextTab
             | Action::GoToPreviousTab
             | Action::CloseTab
diff --git a/zellij-client/src/lib.rs b/zellij-client/src/lib.rs
index 2bfaae2e8..8bb595bc7 100644
--- a/zellij-client/src/lib.rs
+++ b/zellij-client/src/lib.rs
@@ -18,7 +18,7 @@ use zellij_utils::{
     channels::{self, ChannelWithContext, SenderWithContext},
     consts::{SESSION_NAME, ZELLIJ_IPC_PIPE},
     errors::{ClientContext, ContextType, ErrorInstruction},
-    input::{actions::Action, config::Config, layout::Layout, options::Options},
+    input::{actions::Action, config::Config, layout::MainLayout, options::Options},
     ipc::{ClientAttributes, ClientToServerMsg, ExitReason, ServerToClientMsg},
 };
 
@@ -86,7 +86,7 @@ pub fn start_client(
     opts: CliArgs,
     config: Config,
     info: ClientInfo,
-    layout: Option<Layout>,
+    layout: Option<MainLayout>,
 ) {
     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";
     let take_snapshot = "\u{1b}[?1049h";