Quicksettings: add favorite contact tile (2/2)

PS2+3: fix NPE
PS4: add observer to update contact on change

Change-Id: I08b8859fbef4f1ee71b3f6fb259afec3a3829199
Signed-off-by: Dirk Rettschlag <dirk.rettschlag@gmail.com>

Conflicts:
	core/java/android/provider/Settings.java
	packages/SystemUI/src/com/android/systemui/statusbar/phone/QuickSettings.java