Changed good measure count calculation to only consider the validity of...

Changed good measure count calculation to only consider the validity of measures after performing all registrations so as to allow for references that can change their validity.  This fixes #459.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@3608 41f8697f-d340-4b68-9986-7bafba869bb8