BUG: 2816. Made data present in SceneViews to be stored in MRB file even if not present in the main scene.
 Restructured vtkMRMLApplicationLogic::SaveSceneToSlicerDataBundleDirectory() code, made it more modular.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@22325 3bd1e089-480b-0410-8dfb-8563597acbee