Document how to work with SPARQL

Query SPARQL via a utility function: https://github.com/simphony/osp-core/blob/master/tests/test_sparql.py

Query SPARQL via a member function: https://gitlab.cc-asp.fraunhofer.de/simphony/wrappers/allegrograph-wrapper/-/blob/master/tests/test_agraph_city.py#L334