caminfo computations for ParallaxX/ParallaxY and ShadowX/ShadowY were not...

caminfo computations for ParallaxX/ParallaxY and ShadowX/ShadowY were not properly implemented.  Updated documentation with a new example.  Fixes #1296

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@4882 41f8697f-d340-4b68-9986-7bafba869bb8