Modified to attempt to get Target information (frame code and radii) from cube...

Modified to attempt to get Target information (frame code and radii) from cube labels if the given target is not recognized. Placed the following static methods in the Target class: radiiGroup() and lookupTargetRadii(). References #3892. References #3934. Fixes #3940.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@6733 41f8697f-d340-4b68-9986-7bafba869bb8