SystemUI: highlight quick settings and notification clear buttons

Actually make use of the drawables bestowed upon us by the Google

Change-Id: I54ed68cf529eec0a0b76e9e35599d70a7d38f686
SystemUI: Option to display Quick Settings when there are no notificaions

Added member function hasNotifications to class PhoneStatusBar. This
function returns true when notifications are present on the status
bar. Also, onTouchEvent in NotificaionPanelView now flips to Quick
Settings if there are no notifications, and the QS_QUICK_PULLDOWN is
set accordingly.

Change-Id: Ia77f90b19c7b408b7fc9376b6914e3173b734655