ENH: Added 'Crop to reference image geometry' segmentation conversion option

If 'Crop to reference image geometry' is enabled, then when closed surfaces are converted to labelmaps,
the extent of the generated labelmap will be restriced to the reference image extent.
It is useful for importing large models that have irrelevant parts outside the reference image.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@26065 3bd1e089-480b-0410-8dfb-8563597acbee