Intermediate commit for cyrille. Contains the following unfinished business
* reinstatement of the opengl canvas
* new, experimental glsl plugin
* refactored filters listview to use QListWidget & threadweaver
* added a threaded applicator that takes a function and a paint device, devices the paint device in areas and applies the function to each area in a thread
* start with the qpainter image context so we'll share the projection between views that use the qpainter canvas
* apparently some rendering fixes :-)
* cut down a little on the debug output for those who haven't discovered kdebugdialog
* delete the old kisthreadpool: threadweaver is so much nicer, besides, when things don't work, I can blame Mirko instead of myself