Migrate from quoted triples to triple terms

[rubensworks]

Following the changes in w3c/rdf-concepts@6b7ea76, this PR uses triple terms instead of quoted triples.

For the TRIPLE function shorthand, the same syntax was used as in Turtle: <<( ?s ?p ?o )>>

This PR does not yet update the grammar, as I believe this was auto-generated before.
@afs I believe you had such a generator? Could you look into running it for these changes? (also for SPARQL Update I guess)
I guess we can do this in a separate PR from this one.

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Preview | Diff

[afs]

I have a updated grammar in-progress. It includes the current reifier token, multiple reified on stated triples and the multiple annotations work that is now part of Turtle.

It's written - there a few tasks to complete:

• The triples output needs checking - this shows whether the grammar is right or not
• The naming needs to be checked/aligned to the Turtle grammar (QuotedTriple->TripleTerm is done)

[hartig]

Looks good!

[gkellogg]

Fine with this, but we should probably use "reifying triples" in examples, rather than "triple terms".

[TallTed]

[@gkellogg] Fine with this, but we should probably use "reffing triples" in examples, rather than "triple terms".

I'm sure "reffing triples" is a typo.

I think you meant "reified triples" (which are the objects of "reifying triples"), but maybe you meant "reifying triples" (which have rdf:reifies as predicate).