Handle theme changes

Change-Id: Ib933df8ef825ac35dfcf3207be5f803c2da18f56

Conflicts:

	src/com/android/launcher3/Launcher.java

(cherry picked from commit 97564b6e95d10c27c4c97611dc10b5749740308d)
Use theme change categories and clear widget preview cache

Change-Id: If10fa3fa407891b91322c7e982742eb1dfab2b93
(cherry picked from commit e6e927b1216900726b573a6f3008e9e0d56c8444)