Enable moving applications to an external volume

* Always enable moving applications to an external volume if it is
  available and mounted

Change-Id: Ia683eda30338dfad0d7e78087d42d7e512fa83e4

Add app moving setting to the menu in Settings -> Apps

Change-Id: I5fdbc6c46a6ba7f348c0310eb83e96a2784256df
Merge remote-tracking branch 'PA/kitkat' into kitkat-legacy-staging