* Update NQuads::Format#sample to not allow newlines and allow a BNode graph name.
* Update NTriples::Format#sample to not allow newlines.
Added Solutions#- and Solution#disjoint? for SPARQL result set negation (minus operator).
* Solution#disjoint? indicates if two solutions overlap or not.
* Solutions#- filters self by removing any solution from another result set which compatible and not disjoint.