fix for reg-status and voc-der-modes (#191)

* changes to readme and add file for testing sparql endpoint.

* Add support for the sparql endpoint on the pyoxigraph client. supports select, construct and ask.

* integrate changes with updated fix from edmond

* remove commented code and update base class sparql method signature

* add tests for sparql endpoint

* added reg status and vocab derivation modes needed for rendering colors in prez ui. might need to add some color declarations to the derivations. peding advice from david / edmond

* add skos:prefLabel to vocprez default profiles.
Davids recommendation to get the prefLabels returning. but it doesn't work so further changes required.

* add prefLabel to all vocprez profiles.

* still some failing tests

* all tests passing

.gitignore

@@ -6,3 +6,4 @@ __pycache__/
 .pytest_cache/
 .env*
 !.env-template
+rdf/