Fixed warp transform worker : sometimes there were some artefacts where applying the transformation to a paintDevice, due to Qt not being able to describe the transformation
between 2 quads when one of them is degenerate. To fix that, I decided to do the quad interpolation myself, to customize the behaviour when dealing with degenerate quads.
I also added the changes to the preview computations (actually a mix of both methods, because qt's code seems faster than mine).
I also added warp to the tool widget, and redesigned the "free transform" part a bit in the process. Though, the warp part of the widget is not yet connected to the tool itself.


svn path=/trunk/koffice/; revision=1160058