Trebuchet : Support for custom icons per shortcut

Allows user to assign custom icons from icon packs to individual
homescreen shortcuts.

Change-Id: I6613b5f3e6517485a6f83aa5f6769e22bb7f18dc
Merge "Trebuchet : Support for custom icons per shortcut" into cm-10.2
Merge remote-tracking branch 'cm/cm-10.2' into cm-10.2