Define model objects 


git-svn-id: https://source.sakaiproject.org/svn/kernel/branches/KNL-1107@129030 66ffb92e-73f9-0310-93c1-f5514f145a0a
dd impls for model objects and the beginnings of a DAO for RepoItems


git-svn-id: https://source.sakaiproject.org/svn/kernel/branches/KNL-1107@129031 66ffb92e-73f9-0310-93c1-f5514f145a0a