Implement a new free patch deform algorithm

The algorithm should also move the nodes as well. The patch
also implements a new Shift-mode:

Shift+drag-patch --- drags the patch without modifying the handles

The main idea of the algorithm is: it gest the offset budget from
the user's drag and splits it among the following moves:

* translate all four nodes if the patch
* offset the nearest segment
* translate the nearest node (or the two nodes of the nearest segment)

CC:kimageshop@kde.org