-Redone control panel in video detail fragment.

-Added playlist append menu item to channel and playlist fragments.
-Added debouncing to local playlist fragment to allow saving join when list is reordered or item is deleted.
-Extracted hardcoded strings.

app/src/main/res/menu/menu_channel.xml

@@ -22,4 +22,12 @@
         android:icon="?attr/share"
         android:title="@string/share"
         app:showAsAction="ifRoom"/>
+
+    <item
+        android:id="@+id/menu_append_playlist"
+        android:icon="?attr/playlist_add"
+        android:title="@string/append_playlist"
+        android:visible="false"
+        app:showAsAction="ifRoom"
+        tools:visible="true"/>
 </menu>

app/src/main/res/menu/menu_playlist.xml

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="utf-8"?>
 <menu xmlns:android="http://schemas.android.com/apk/res/android"
-      xmlns:app="http://schemas.android.com/apk/res-auto">
+    xmlns:app="http://schemas.android.com/apk/res-auto"
+    xmlns:tools="http://schemas.android.com/tools">
 
     <item
         android:id="@+id/menu_item_openInBrowser"
@@ -12,4 +13,12 @@
         android:icon="?attr/share"
         android:title="@string/share"
         app:showAsAction="ifRoom"/>
+
+    <item
+        android:id="@+id/menu_append_playlist"
+        android:icon="?attr/playlist_add"
+        android:title="@string/append_playlist"
+        android:visible="false"
+        app:showAsAction="ifRoom"
+        tools:visible="true"/>
 </menu>