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
```

8 files changed, 231 insertions, 217 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