DeskClock: Add back flip and shake actions

Cherry-picked and ported from:
 * http://review.cyanogenmod.org/#/c/29894/

Change-Id: I222b6cd53a95db6f8662e7aef52aa6922d8a5d6a
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>

Conflicts:

	res/values/cm_strings.xml
	res/xml/settings.xml
	src/com/android/deskclock/SettingsActivity.java