Non-rdf resources emit /fcr:metadata events instead of /jcr:content

Fixes https://www.pivotaltracker.com/story/show/81279166
I'll swap in the JCR_CONTENT and FCR_METADATA constants.

I'm not sure precisely what the current behavior is, other than to say that the message consumer expects the event to point to RDF instead of the binary, which is why I was updating the jcr:content events to point to fcr:metadata instead of to the binary itself.