Launcher3: Icon pack support

Some love for Launcher3 users
based on CMs Trebuchet and Burger

PS4
Add iconMask/iconBack/iconUpon/iconScale support

Change-Id: I2c3d29cfbceca060defd53980244e90dc46eb322

Conflicts:
	res/values/gummy_strings.xml
	src/com/android/launcher3/IconCache.java
	src/com/android/launcher3/LauncherPreferences.java
	src/com/android/launcher3/Utilities.java