DeskClock: Add back user-defined world cities

Ported from:
 * http://review.cyanogenmod.org/#/c/33001/
 * http://review.cyanogenmod.org/#/c/44805/

Patchset 2: Rebase dependency

Change-Id: Iefbf8fa2c3d0d537d85cf734300f3ce2df6ae315
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>