Changed property "nodeTypes" of OutputCheckerboardComboBox to "vtkMRMLScalarVolumeNode" to fix crashing.

It is now possible to create the output volume from within the module.
Movie kind of works.

Until now only red slice works. View must be axial.
Movie works for all three SliceWidgets.

Several changes regarding the UI were necessary to enable the user to choose which SliceWidget should show the Movie.