Added measure type, line, and sample filters. Added a couple of existing...

Added measure type, line, and sample filters. Added a couple of existing filters to the image-point filter selector and fixed typos in a few of the filter description strings. Fixes #645.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@3924 41f8697f-d340-4b68-9986-7bafba869bb8