Camera.h: 2011-02-10 Jeannie Walldren - Moved code from LoadCache() methods to...

Camera.h: 2011-02-10 Jeannie Walldren - Moved code from LoadCache() methods to create new methods CacheSize() and StartEndEphemerisTime().  Removed unused input parameter from LoadCache(). Set pointers to null in constructor. Added documentation to methods, enum, and private variables. 

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@1697 41f8697f-d340-4b68-9986-7bafba869bb8