replace "filter(s)" in most running text with "`FILTER` clause(s)" including that codefence

[TallTed]

Originally posted by @hartig and @TallTed in #257 (comment)

[@TallTed] (I note that "filter" and "FILTER" were treated inconsistently in SPARQL 1.1 Query Language. I think "filter" should be avoided as a noun, and should generally be replaced by "FILTER clauses", always including the codefence around FILTER.)

[@hartig] Yes! But that is something to be implemented in a separate PR.

Agreed.

This issue is to track its implementation at least within sparql-query.

Might be we need a distinct issue, or at least a distinct PR (tracked by a to-do list here or elsewhere), for each RDF & SPARQL 1.2 document.

[afs]

I think "filter" should be avoided as a noun, and should generally be replaced by "FILTER clauses",

I don't think it is so simple.

Use "FILTER clauses" when it's specifically about the syntax (which is where clauses are).

Don't write FILTER when referring to the concept or in the algebra/evaluation items of that name and link to relevant "filter" definition.

[TallTed]

Much as with MUST and must, filter is easily misread as FILTER, though perhaps this will be minimized if careful attention is paid such that code fences, upper-/lower-case, and "clause" suffix are applied correctly throughout.

Still, wherever possible, if "FILTER clause" is not appropriate, I think using another word would be better. Candidates are probably context-dependent.