Fix and improve service switching (introduced colors)

- Every service now have its own colors
- Fix bug navigation button and backstack count
- Fix and themed properly the icons and colors of the main fragment tabs
- Re-organized the styles and colors (too much in one file)

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

@@ -1,5 +1,14 @@
 <?xml version="1.0" encoding="utf-8"?>
 <menu xmlns:android="http://schemas.android.com/apk/res/android">
-    <item android:title="@string/youtube" />
-    <item android:title="@string/soundcloud" />
+    <group
+        android:id="@+id/menu_services_group">
+        <item
+            android:id="@+id/menu_service_youtube"
+            android:icon="@drawable/youtube"
+            android:title="@string/youtube"/>
+        <item
+            android:id="@+id/menu_service_soundcloud"
+            android:icon="@drawable/soundcloud"
+            android:title="@string/soundcloud"/>
+    </group>
 </menu>