Initial commit for App Switcher docs

docs/apps.asciidoc

@@ -0,0 +1,12 @@
+[[kibana-apps]]
+== Kibana Apps added[4.2]
+
+The Kibana UI serves as a framework that can contain several different applications. You can switch between these 
+applications by clicking the image:images/app-button.png[App Picker] *App picker* button to display the app bar:
+
+image::images/app-picker.png[]
+
+Click an app icon to switch to that app's functionality.
+
+Applications in the Kibana UI are managed by <<kibana-plugins,_plugins_>>. Plugins can expose app functionality or add new
+visualization types.

docs/plugins.asciidoc

@@ -1,5 +1,5 @@
 [[kibana-plugins]]
-== Kibana Plugins
+== Kibana Plugins added[4.2]
 
 Add-on functionality for Kibana is implemented with plug-in modules. You can use the `bin/kibana plugin` 
 command to manage these modules. You can also install a plugin manually by moving the plugin file to the 
@@ -120,3 +120,14 @@ path to that configuration file each time you use the `bin/kibana plugin` comman
 64:: Unknown command or incorrect option parameter
 74:: I/O error
 70:: Other error
+
+[[plugin-switcher]]
+== Switching Plugin Functionality
+
+The Kibana UI serves as a framework that can contain several different plugins. You can switch between these 
+plugins by clicking the image:images/app-button.png[Plugin Chooser] *Plugin chooser* button to display icons for the
+installed plugins:
+
+image::images/app-picker.png[]
+
+Click a plugin's icon to switch to that plugin's functionality.