CM11 Themes: Add support for composed icons [2/2]

Requires f/b patch http://review.cyanogenmod.org/#/c/65179

Change-Id: Id9dd024448ddab41ef92177cf0d4cbc9abea0523
Remove all icons in onPreExecute()

Until the icons are loaded, we should show nothing in the icons
container.  This prevents users from seeing the wrong icons in
the view before they are loaded.

Change-Id: I9c0ec7df2cc9ed8a15012f47d9b4aa3caf8bb412