Fixed control net reader to work with networks that don't have any points;...

Fixed control net reader to work with networks that don't have any points; removed old Qt model-view code from cneteditor; cneteditor does not try to get a reference measure if there isn't one

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@2939 41f8697f-d340-4b68-9986-7bafba869bb8