[vtkusers] Added QVTKRenderWindowInteractor.py

[Jody Winston]

Prabhu Ramachandran writes:
 > hi,
 > 
 > I managed to get a QVTKRenderWindowInteractor.py working based on the
 > David's QVTKRenderWidget.py.  I just committed it and its in the
 > vtk/qt/ directory.  This completes the interactor based widgets for
 > all the presently supported Python widgets.  It seems to work fine for
 > me but YMMV.  Note that just like QVTKRenderWidget it is supposed to
 > work only under *nix and not under Win32.
 > 

What work is necessary to have this new interactor work on Win32?