BUG: Fix volume rendering object factory on VTKv6

Issue #3514

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23142 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: Fix VTK python library paths on Windows for VTKv6

Issue #3514

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23143 3bd1e089-480b-0410-8dfb-8563597acbee