Lockscreen Notifications: Custom background color [1/2]

Change-Id: Id5f950a0f6e526b46c0662d14a1b8ca664c0b4f8

Conflicts:
	core/java/android/provider/Settings.java
	packages/Keyguard/src/com/android/keyguard/NotificationHostView.java
	packages/Keyguard/src/com/android/keyguard/NotificationViewManager.java