Remove some duplicate code which ControlPointEdit was handling, fix bug which...

Remove some duplicate code which ControlPointEdit was handling, fix bug which caused seg fault when deleting a point using middle mouse click after creation of ground point.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@4359 41f8697f-d340-4b68-9986-7bafba869bb8