Added (pure) virtual methods CkFrameId(), CkReferenceId(), SpkTargetId(),...

Added (pure) virtual methods CkFrameId(), CkReferenceId(), SpkTargetId(), SpkCenterId() and SpkReferenceId(); removed SetCkFrameId() and SetCkReferenceId() as new methods obsolete them; fixed bug in computations of North, Sun and Spacecraft azimuth angles when shape models are present

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@1512 41f8697f-d340-4b68-9986-7bafba869bb8