Initial work to use a more general rdf database

Instead of making a graph database on top of our pgdoc, this
experiment should create a general rdf database that is capable
of having full JSON Documens as the Value in the RDF triplet.

So we could insert things lik

resource res:1234 have subjects:ContactInfo with a value {
  Phone: "xxx-xxxx-xxx",
  Label: "residential phone"
}
Working RDF data insert
Fetching a single resource via url
Experimental rdf client api.
A client API for rdf store