[pyramid] add routes /{eid} and /{etype}/{eid} to return RDF when rdf mimetype in Accept HTTP headers
* simplify pyramid/resources.py by making the classmethod that returns a closure
a simple function and removing the EntityResource and ETYpeResource classes
that are barely used
* replace predicate MatchIsETypePredicate with MatchIsETypeAndEIDPredicate
Team: famarger, schabot, nchauvat, fferry, ethieblin