Settings: allow device trees to invoke custom display settings

in this case gesture control settings.

Intent used: com.slim.action.LAUNCH_SCREEN_OFF_GESTURE_SETTINGS

Change-Id: I82f5a8a4075f109419b08014ad2d723bf2f54402

Conflicts:
	res/xml/display_settings.xml
	src/com/android/settings/DisplaySettings.java