New digital clock widget for Clock

Bug: 7390795

Added a new widget with its own provider and service and factory.
Factory extends a broadcast receiver and listens to all time
changes, locale changes, changes in world clock and alarms.
Added broadcasts for changing the world clock's user cities list
and for setting the next alarm.

Change-Id: Ida4bbd619da941fb46505cb2ac653fde0a41a97f