Finish integration of serializers and deserializers in the codebase

This branch gets some things going:

• It adds serialization and deserialization support for the JSON-LD format. Downsides: ATM it's probably a subset, and it's definitely uglier than the really nice JSON-LD currently produced by tracker_resource_print_jsonld()
• It adds an internal helper to deserialize TrackerResources into cursors
• It adds a tracker_resource_print_rdf() that takes a TrackerRdfFormat enum, and allows printing a resource in all RDF formats that we support.
• It deprecates tracker_resource_print_turtle() and tracker_resource_print_jsonld(), in favor of tracker_resource_print_rdf()
• It implements https://www.w3.org/TR/2013/REC-sparql11-service-description-20130321/ on our HTTP endpoints, providing basic RDF to describe our HTTP endpoints.

This should finish all remaining items at #359 (closed)