Fix searching organisations by name and ID

When searching organisations by name, use both the
http://www.w3.org/2004/02/skos/core#prefLabel and the
http://xmlns.com/foaf/0.1/name fields.

See 
http://api.lobid.org/organisation?name=hbz
http://api.lobid.org/organisation?id=DE-605
http://api.lobid.org/organisation?name=Stadtbibliothek+Bo&format=ids