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/layout/fragment_main.xml

@@ -11,7 +11,7 @@
         android:layout_width="match_parent"
         android:layout_height="wrap_content"
         android:layout_alignParentTop="true"
-        android:background="@color/dark_youtube_primary_color"
+        android:background="?attr/colorPrimary"
         app:tabGravity="fill"/>
 
     <android.support.v4.view.ViewPager