1. ENHANCED: Also remove the mapped onto blank node when removing an RDF term, if present.
2. ENHANCED: RDFS builders allow the graph argument to be uninstantiated (for assertion in graph `user`).
3. ENHANCED: RDFS isDefinedBy automatically links to registered RDF prefix IRI, if available.
4. ENHANCED: RDFS seeAlso can be asserted of literals using the blank node mapping.
5. ADDED: RDFS class removal, keeping the class hierarchy intact.
6. ADDED: IRI to RDF prefixed IRI converter.
7. ENHANCED: Use mutexes for blank node mapping.