Improve and simplify fcr:versions response triples to have links only.

https://www.pivotaltracker.com/story/show/70475058
There are two cases of using the fcr:version response triples, one is the html output that need a full version of the RDF triples, another is the RDF response that need improve. As we discussed during the standup meeting this morning, I've separated the html response to have its own rest api method, and filtered the fcr:version triples for the RDF response to contain only the links to the versions.