TODO
----
[x] Facture out graph stuff from emmo.ontology.py
[x] Facture out controlled vocabulary stuff from emmo.ontology.py
[ ] Make documentation
[ ] Inject properties in Owlready2.entity.ThingClass
    [ ] annotations
    [ ] ... <current methods in emmo.Ontology that takes an entity as argument>
    [x] EMMO-relations
[ ] Update the relation branch in EMMO - it does not correlate with the
    relations actually used...
