Launcher3: Do not react to Menu button when in 'All apps' mode

Avoid entering overview mode while in 'All apps' mode.

Change-Id: I39d006569f4f0d4f6eb521cdad4e475430337a3f
Handle theme changes

Change-Id: Ib933df8ef825ac35dfcf3207be5f803c2da18f56
Use theme change categories and clear widget preview cache

Change-Id: If10fa3fa407891b91322c7e982742eb1dfab2b93