Associate RDF schemas within the user schemas

[sblack-usu]

Currently, the association of an rdf schema with a user-friendly schema is done through a utility function. This association should be baked into the user-friendly models allowing the user-friendly models to read/write an rdf/xml file through a single method call.

Acceptance Criteria:
An rdf/xml file can be read into a user-friendly schema from the user-friendly schema directly