for preview: retrieve info descriptions (SKOS, schema.org)

[andresgruber]

For linking datasets other then dbpedia, the preview should be able to fetch descriptions and depictions as well.

• For SKOS vocabularies it should fetch the respective properties. As there is no explicit property for depiction, I would choose "skos:notation" and "skos:definiton".
• For schema.org, it should retrieve: "schema:name" and "schema:thumbnail".