Add more descriptive fields to ResourceConfig

[jesper-friis]

OTEAPI is supposed to be used to document data sources and sinks. For that purpose it would be useful to have more descriptive fields in ResourceConfig.

The ResourceConfig already has some non-technical fields like license, accessRights and publisher. It would be useful to also add the following fields (found in the dcterms and rdfs namespaces):

• description
• conformsTo
• requires
• comment