Fixes #625 - Changed ground azimuth algorithm from using Napier's analogies to...

Fixes #625 - Changed ground azimuth algorithm from using Napier's analogies to using the spherical law of cosines for sides

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@3938 41f8697f-d340-4b68-9986-7bafba869bb8