[Feature] Provide Graph database incorporational functionality

[omaus]

For everyday use, parsing of ontological files and working with their in-memory object is doing the job. But when working with a large database of ontological terms, it might be nice to have functionality accessing those databases (e.g. Neo4j, GraphDB) and performing queries on them.
This means just that people use functions like e.g. Ontology.getTerm and get the query result parsed as CvTerm.

(Idea credits: @Freymaurer)