Interactor style

I created new InteractorStyles to handle zoom, edition, the cross tool, window level & width in the viewer_slice. The idea is that each new functionality be added as a new InteractorStyle instead of being added directly the viewer_slice. When the method SetUp is defined in the InteractorStyle, that method will run prior to InteractorStyle starts working. It's possible CleanUp after the InteractorStyle be used.