overlapstats.xml: Added check to ensure the provided cube list is the same one...

overlapstats.xml: Added check to ensure the provided cube list is the same one used in findimageoverlaps (i.e. the serial numbers in the overlap list match the serial numbers in the provided cube list). Fixes #515. 

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@3804 41f8697f-d340-4b68-9986-7bafba869bb8