* [RDF_TABULAR,NEW] Added rdf_tabular_quads//5. Also, rdf_tabular_triples//5
  no longer displays the graph column (but the quads variant does).
* [RDF_TABULAR_DATATYPE,EXT] Do not show table for 0 rows.
* [RDF_TABULAR_GRAPH,NEW] Added RDF prefix widget.
* [RDF_TABULAR_GRAPH,FIX] Explicitly characterize RDF graph.
* [RDF_TERM_HTML,NEW] Very simple HTML generation for RDF prefixes.