(Bug 42063, bug 44577) RDF for Special:EntityData

Special:EntityData supports RDF/XML output when using the .rdf postfix and N-Triples output when using the .nt postfix.
EasyRdf ( http://www.easyrdf.org ) is introduced for easy modeling and exporting of the data model as RDF.

Patch by Anja Jentzsch, Thomas Pellissier Tanon, Daniel Kinzler

Change-Id: Ie9f2f8944a65750077152a69923c0a0b18a49d5e
Merge "(Bug 42063, bug 44577) RDF for Special:EntityData"