ENH: test adding storable data after a scene view is created

Add a fiducial, store a scene view, add a volume, restore the scene view.
To conform with the current implmentation, the new storable node
should not be present after the scene view is restored.
The test pops up an info window which times out after 15s (needed
during run time to let the user read it).

Issue 0003956

git-svn-id: http://svn.slicer.org/Slicer4/trunk@24386 3bd1e089-480b-0410-8dfb-8563597acbee