add support for building flashable kernel zips

choose device from lunch menu then enter make bootzip, builds flashable boot.img with updated source ramdisk

Change-Id: I07820d5e5e48d5b973901ed2bb3f330744c6498c

Conflicts:
	core/Makefile

Conflicts:
	core/Makefile
Merge branch 'cm-11.0' of https://github.com/AxxionKat/android_build into cm-11.0