Statusbar slide brightness control

This allows the ability to control brightness by sliding across the statusbar.

Patchset 2   : Cleanup as per suggestions.
               Removed duplicate key from Settings, after settings merge
               Reduce mLinger threshold (Need feedback on whether its too sensitive for some)
Patchset 3,4 : Minor cleanup
Patchset 5   : Cleanup as per comments
Patchset 6   : Remove unused import
               Avoid unecessary gc of unchanging variables (make them instance variables)
Patchset 7   : Cleanup

Change-Id: I19ee7de07be7bfeabde3fb2ae3c60ebdbb4afd72