Added termcombination field in triple tables (used to facilitate term roundtripping - can be used as an additional index).  Added REGEXTerm support.  Completed contexts method (with triples)
Added termcombination field in triple tables (used to facilitate term roundtripping - can be used as an
additional index).  Added REGEXTerm support.  Completed contexts method (with triples)

Letractively/rdflib,Letractively/rdflib,Letractively/rdflib