Replace stretched background textures with real gradients

Change-Id: I320733aaef191318d32fa823d9a6140585f49417
Signed-off-by: Chet Kener <Cl3Kener@gmail.com>

Conflicts:
	core/res/res/drawable-nodpi/background_holo_dark.png
	core/res/res/drawable-nodpi/background_holo_light.png