Fixed bug causing inconsistencies between runs of the program and line-sample...

Fixed bug causing inconsistencies between runs of the program and line-sample of Control Measures within Control Points due to using the Point's radius when RETRIEVAL=POINT.  The program now uses the DEM of the cube being added to compute the radius, and thus more accurately reflect the line-sample corresponding to a point's latitude-longitude.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@3009 41f8697f-d340-4b68-9986-7bafba869bb8