STYLE: Simplify qSlicerModelsModuleWidget introducing vtkNew smartpointer

Using vtkNew avoid to manually manage reference and simplify the
code.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23541 3bd1e089-480b-0410-8dfb-8563597acbee
COMP: Update Datastore to fix build introduced when trying to fix warning

See Slicer/Slicer-DataStore@713f1f8

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23542 3bd1e089-480b-0410-8dfb-8563597acbee