BLUEPRINT RDF Support

In order for Odysseus to read the SKOS resources that'll power it's bookmarks, Prosody must learn to read RDF. In terms of syntax Prosody properties would be mapped to RDF predicates, and iteration would give all RDF objects that match that predicate path. Just throw in a new template tag to define XML & RDF namespaces, and we should have all we need.

The only problem is with whether the predicates we're matching are explicit or implicit, and supporting implicit would both be easier at the UI level and more correct. For this I'd add a component I'll call Pallas.