[1/2] SystemUI: Add time-context headers to the notification header

This commit adds image headers to the notification panel header,
based on the date/time. There are pictures for morning, afternoon
and night, as well as special events like Christmas and new
year's eve.
More will be coming, with eventually a way to use an external
(as in, Internet) provider for those pictures.

Change-Id: Ie3321e9a3e0637d6ba8094dd46aee36c41354713
base: wait for system ready before calling button timeout

Else we will get a NPE

Change-Id: I529230c8655f6f55358ac206d8df0527e733799c
Merge "[1/2] SystemUI: Add time-context headers to the notification header" into android-4.4