Linking to datastream fcr:metadata in HTML UI

Fixes https://www.pivotaltracker.com/story/show/80952408
Both -- I don't think I'll have time to implement the JS version, but I also think the Javascript approach is very convoluted.  I also think the fact that the user sent an Accept header asking for HTML (and did not specify a Prefer header) is reason enough to alter the triples that get returned.