grouper: Better background gradients

Now lots of backgrounds look a bit ugly.
Using another dithering mode produces better gradients

Change-Id: Id19686e47861340c322c67c94c398699af502a85
F2FS for /data to improve IO Performance (2/2)

See (1/2) for explanations

Change-Id: I5afbd266d93eca401d2200e9342e589f2364852f

Conflicts:
	arch/arm/configs/slim_grouper_defconfig