New switch -b to create desktop blur effect.

 o Takes a screenshot of the desktop, blurs it and creates
   a top level window on top of everything else. Apps started
   afterwords will be unblurred.
 o kdesk -b will work as a toggle switch
 o Needs more work to integrate this into a signal and remove taskbar icon.
Adding kdesk -b switch to send a blurring effect signal

 o the flag will use Kdesk's built-in signaling system
   to create a toggle blur effect, provided by the
   background class.
Updated important source comments that need attention
Merge pull request #43 from KanoComputing/blur

New switch -b to create desktop blur effect.