Document when http://www.w3.org/2007/ont/link#uri statements are added #221
Description
It seems that when there is an owl:sameAs statements rdflib.js adds a statement with the predicate http://www.w3.org/2007/ont/link#uri pointing to a literal with the same value as the IRI to which the owl:sameAs statement points. It would be nice to have this behaviour and its rationale documented.