Parse WHERE clause using ANTLR

[Qup42]

Parse whereClause in ANTLR. This is one fairly big connected chunk of the grammar.

The parsing should already work. It is live in the SparqlParser.

TODO:

• more Tests
• negative Tests
• Combine std::pair<...> return types into structs.
• Research valuesClause

[joka921]

This already looks very nice. I gave it a first long round of reviews, let me know when you want to talk about any of it.

[joka921]

Very nice, this is really getting in shape.
I have left some remarks, and some of this we should maybe discuss in person.
But I think you should have enough to do:)

[joka921]

This is almost done. We have already tried this out yesterday and especially @hannahbast liked it very much. There is one slight issue with the new way you call addLanguageFilter but that is because that function was always kind of broken and will already be fixed before this gets merged (not your fault).

[joka921]

Really nice,
I think we are converging towards merging:)

[joka921]

Great! This is a very important milestone towards more correct and cleaner parsing!

[hannahbast]

@Qup42 BTW, I already told Johannes, but I didn't tell you yet, Julian: Thank you very much for your work on this PR and the associated ones! It's a major milestone for QLever. In particular, it allowed me a happy update of this page: https://github.com/ad-freiburg/qlever/wiki/Current-deviations-from-the-SPARQL-1.1-standard . And it's the basis for many other improvements that had to wait so far because we didn't have a proper SPARQL parser.