*New version of undo/redo feature
	- improves memory management
	- works with 3d magic wand
	- Removes undo/redo stacks when view closed
	- works with copy/paste slice feature
*vtkCircleCursor not activated with CTRL anymore (see commented line in
v3dView)
* Improvements for copy/paste slice feature
	- Corrects bug occuring when no view is opened