Support SPARQL-star specification

[damooo]

Sparql-star allows us to work with quoted triples that are supported in RDF-star, nd have analogous "triple terms" in RDF 1.2

It would be great if qlever has support for them

[damooo]

For example, apache jena too supports it.

[ktk]

RDF Star (& SPARQL-Star) is not a thing yet as RDF 1.2 is not published yet. What Jena does is give a sandbox of the current spec. We surely won't start before it's final and while it's on the roadmap, it does not have high priority at the moment.

This might change in case we find a (paying) customer that needs it.