[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
Changed contextual notification panel headers

See images - http://i.imgur.com/PupEJ5p.jpg

Change-Id: If848d162523610946c317919d2f6664d891906e6
Add evening time to header

Scaled all images

Change-Id: I5d9a41d92803d64f67cf2fb9dd2c4294a947efc3