The crashes were caused by incomplete refactoring: dockers used to be
owned by the view, now they are owned by the main window. In order to
facilite finishing the refactoring, I have moved all dockers out of
krita/ui into a default dockers plugins, then I fixed all dockers to
behave properly.

* the palette docker now integrates with the KoCanvasResourceProvider
* the bird's eyeview docker is cleaned up and no longer is deleted when
the view is delted
* the histogram docker is temporarily disabled (will be re-enabled in
step 2
* the layer docker is cleaned up, is now a client of the canvas instead
of the view and is notified when the canvas is updated
* KisCanvas2 has a new signal that is emitted whenever the image is
changed

svn path=/trunk/koffice/; revision=1031900