Make KeyguardMultiUserAvatar fully themeable

Create the animation color for the username text based on the final
color.

Change-Id: I4b1beb70160e178264c32f3b33c6c0c7c51f70c5
Signed-off-by: Dirk Rettschlag <dirk.rettschlag@gmail.com>

Conflicts:
	packages/Keyguard/src/com/android/keyguard/KeyguardMultiUserAvatar.java