Add a SPARQL check to make sure shacl namespace prefixes are bijective

[cmungall]

It is useful to serialized prefix expansions using the SHACL vocabulary.

Many obo format ontologies that refer to non-OBO classes will start doing this:

• https://github.com/owlcs/owlapi/pull/1072

But I think this is broadly good practice

It would be handy to have a check to make sure prefix maps are 1:1. Perhaps ERROR for prefix clash and WARN for namespace clash.

It may also be useful to have some options when doing merges to prioritize one ontology over another but that should be a separate issue