Corrected issues with Apollo dataset; user comments are now added to kernel...

Corrected issues with Apollo dataset; user comments are now added to kernel comment section rather than replacing them; Added OVERLAP parameter to provide control over start/end time conflicts; support both type 9 ad 13 SPK kernels. Fixes #739.

git-svn-id: http://subversion.wr.usgs.gov/repos/prog/isis3/trunk@5769 41f8697f-d340-4b68-9986-7bafba869bb8