Extend describo with more vocabularies

[michaelgfalk]

step 3 - possible future work

This work basically paves the way for extending schema.org with any number of existing ontologies and definitions. RO-Crate already references a number of ontologies in a general sense but the specific properties and classes are not known to describo. Depending on how we go with this first task, we might find an easy, programmatic way to get all of these ontologies and others in for use.