new rdf_list implementation
add [x] = y for rdf:list
a little closer on the rdf:list implementation; still need to work out URI/bnode to RdfList
RDF datastreams now return Date objects for dates
remove some older rdf stuff
freezing rdf_datastreams
more frozen rdf; alter some tests on rdfxml
re-namespace rdf work; remove controlled vocabs, extracting to gem
RDF models aren't strict in new implementation, they fall back gracefully to better support external LOD
fix a few indexing things
more corrections to date handling in rdf tests