Add an empty stub status bar service implementation

For kiosk-type devices that do not present any navigation UI.  This allows
for clean selection of the implementation based on resource overlays,
without the need for the tablet or phone status bar implementations to
accomodate the desired behaviors.

Bug 5824373

Change-Id: Idcec70eef437904edda452b69e5eb7a3cc7094f7
(cherry picked from commit 5717f809 in ics-aah)

Signed-off-by: Mike J. Chen <mjchen@google.com>