* [CACHE_IT,EXT] Caching now works for variable graph.
* [DBPEDIA_EQ,EXT] Calculate whether something is an entity or quantity.
* [MATH_EXT,FIX] average/2 of no number.
* [RDF_READ,NEW] Rewrote rdf2/4 as rdf/5, adding options for how the graph argument is used.