First pass at thick triples prototype

[jamesaoverton]

Working from the Thick Triples Examples Google Sheet and the Thick Triples Design Google Doc, this implements proofs of concept for:

• thin triples to subjects map
• render subjects map as indented lines
• subjects map to thick triples
• predicates map to OWL Functional S-Expression (OFS): ["ObjectSomeValuesFrom", "ex:part-of", "ex:bar"]
• OFS to Manchester (OMN) with labels: 'part of' some Bar
• OFS to HTML+RDFa, e.g. OMN with labels and links
• thick triples to HTML+RDFa

OWL axiom annotations and RDF reification aren't yet supported.