Moar clean options!

appclean: clears out all apks
imgclean: clears out all img files
kernelclean: clears out all kernel stuff
systemclean: clears out all system stuff
recoveryclean: clears out all recovery stuff
rootclean: clears out all root stuff

Change-Id: I3b6d9ca53e083385cca3ae66084c5a39901b3d1b