Look into Gordian for possible graph serialization

[chrysn]

It's a long shot, but I should look into whether Gordian has anything to offer in terms of ready-made serialization of graphs in CBOR.

We probably won't want to afford any large overheads, but that may not be the case -- I'll know when I've looked into it.

The numeric reduction Gordian pulls in through dCBOR is somewhat off-putting, but at least for the use case where it disturbed me the most (round-tripping RDF data), at least my go-to courpus of RDF data has all its numeric values more strictly typed anyway (eg. as ^^<http://dbpedia.org/datatype/kilometrePerSecond> or ^^<http://www.w3.org/2001/XMLSchema#nonNegativeInteger>, so it'd "just" need one more relatively rarely used tag for "I mean float", which we'd need anyway because XSD differentiates between float and double.