BUG: Update MultiVolumeImporter to fix DICOM.instanceUIDs initialization

See fedorov/MultiVolumeImporter@fb38cbbd00

From: Andrey Fedorov <fedorov@bwh.harvard.edu>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23543 3bd1e089-480b-0410-8dfb-8563597acbee
BUG: Update MultiVolumeExplorer to fix issue due to missing cast to int

See fedorov/MultiVolumeExplorer@f9222a25a
and fedorov/MultiVolumeExplorer@9135996ae

From: Andrey Fedorov <fedorov@bwh.harvard.edu>

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23544 3bd1e089-480b-0410-8dfb-8563597acbee