Settings: Heads Up background color && transparency [1/2]

PS12: squash dependency - heads up settings now under interface menu

PS: add ability to set custom heads up text color

Change-Id: I606bf35d5db9a253448971bdedf6fdb3acad6452

Conflicts:
	res/values-es/slim_strings.xml
	res/values-pl/slim_strings.xml
	res/values/slim_strings.xml
	src/com/android/settings/slim/NotificationDrawerQsSettings.java