InCallUI: Add transparency to Glowpad background

this adds transparency to the glowpad view background so the incoming caller's entire picture can be seen.
PS8:making it a preference.

PS16: Permissions

Change-Id: I33bfdc6ed641770a4e0ceb7841e0908581256757

Conflicts:
	res/values-holodark/colors.xml
	res/values/colors.xml
	src/com/android/incallui/CallButtonFragment.java