Refactor CRUD in FedoraNodes and FedoraContent for transparent hierarchy support 

https://www.pivotaltracker.com/s/projects/684825/stories/71230608
My local tests showing that the CRUD operations for objects and files are working as expected now. So I think we are ready to move ahead to evaluation the transparent auto-hierarchy feature. Noted that as mentioned during the standup meeting this morning, there are several existing test cases in FedoraNodesTest and FedoraContentTest classes are failed and ignored at this time, which produce a NullPointerException.