* [DATACUBE,FIX] RDF prefix expansion does not work in lambda expressions
  and/or maplist.
* [RDF_BUILD,EXT] Added subpaths argument to rdf_create_next_resource/4.
* [RDF_NAME,FIX] Explicitly characterize RDF graph.
* [RDF_PREFIX,NEW] Rewrote rdf_prefixes/[1,2] to rdf_prefixes/5:
  * Arbitrary instantiation pattern (now: (?,?,?,?);
    was: (-,-,-,-) and (-,-,-,+)).
  * Prefixes are returned sorted by number of terms that use them.