ENH: move duplicated code into volumes logic

Both the Editor and LabelStatistics modules had code to check
that volume geometry matched for a label map.  The duplicated
code is removed and there is a test in LabelStatistics.

git-svn-id: http://svn.slicer.org/Slicer4/trunk@23406 3bd1e089-480b-0410-8dfb-8563597acbee