An Instrument group is no longer required in the MATCH cube to run the...

An Instrument group is no longer required in the MATCH cube to run the application.  If no Instrument group is found, the output Control Network will simply have no target.  Be aware that this can cause problems when attempting to use this network outside the coreg world.  This change fixes #359.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@3086 41f8697f-d340-4b68-9986-7bafba869bb8