add recommended property to distribution to specify used model(s)/ontology(s)

[coret]

Add recommended property to specify the used model or ontologie (can be multiple) used in the dataset, eg. https://personsincontext.org/model/

There seems to be no appropiate property in schema.org/DataDownload, in dcterms there's conformsTo.

Example triple (from MVP Europeana, aggregating-lod-mvp graph in datasetregister triplestore):
<https://archief.nl/id/dataset/foto/2-10-62ntfoto-loda-edm-distributie> <http://purl.org/dc/terms/conformsTo> <http://www.europeana.eu/schemas/edm/>

[ddeboer]

For the missing schema:conformsTo, see schemaorg/schemaorg#1516 and https://ec-jrc.github.io/dcat-ap-to-schema-org/#conformance.