Revert "Launcher3: Icon pack support"

* The new theme engine handles icon packs, no need for launcher-specific support

This reverts commit 7d6bd88bd7ac6c99753c985468341caff0842a2b.

Change-Id: Ieccfdd850725d01d97ab9dd982102abd72ef2a3e
Revert "Use ArrayListExtra for broadcasting theme changes [2/2]"

This reverts commit ebf8f37515c23a167cef2bb8cff04854c52fd35b.

Change-Id: If80e3bc0443fa9e79c085e9251f4be0a10730397
Revert "Use theme change categories and clear widget preview cache"

This reverts commit b52694e4fdd3c8ee524b5f6f870697e40061b2a6.

Change-Id: I69bff363280ea69ee83dea3a8f2ef2d0d95a7be0