In InterestOperator, added a try/catch to InterestByPoint(). In cnetref,...

In InterestOperator, added a try/catch to InterestByPoint(). In cnetref, changed error handling such that when an error occurs, this program will not choose that measure as reference instead of throwing an error and stopping. In PolygonTools, added a check in LatLonToSampleLine() to make sure the linear rings used to create polygons are closed. Fixes #825.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@5085 41f8697f-d340-4b68-9986-7bafba869bb8