DGraph has to support IRIs for queries as by the spec

[the42]

Currently DGraph doesn't allow predicates (subjects too?) to contain all of the allowed characters as defined by the specification.

As DGraph loads data from triples/quads it should be equally possible to query/retrieve these elements which were also accepted for loading/import.

[manishrjain]

Once v0.7 release is done, I'll work on moving RDF stuff to ANTLR grammar. Will tackle this as part of that change.

[manishrjain]

ANTLR is slow, so we'll just have to do this as part of the Go codebase.