Enable datatype normalisation that is required by at least one jsonld test

This pull request customises the test parsing code so that it links filenames to both fatal and non-fatal errors. It also enables normalisation of datatypes where possible, but does not fail if the normalisation fails. Normalisation is only attempted if the datatype is valid for the literals value.

The errors now also highlight the jsonld tests that rely on blank node predicates that are not supported by either RDF-1.1, RDF-1.0 or Sesame. I didn't ignore these tests, (toRdf-0078 and toRdf-0108), but they are currently incorrectly passing, as both Sesame Models (from N-Quads and JSON-LD) are empty after the test, so they are trivially equal.