Separating ontologies and schemas

[jamesamcl]

CC @cmungall

OLS is hosting not just ontologies but some "ontology-like" artefacts which are more like schemas. Examples: schema.org, biolink, mixs, new requests such as https://github.com/EBISPOT/ols4/issues/1038

They are biomedically useful and ontology-shaped enough for OLS to be a good place to host them. However ideally these would be on a separate "Schemas" tab and solr boosted lower than ontologies to avoid polluting the search.