Lucene query docs, fixing QueryStringQueryProvider (Lombiq Technologies: OCORE-93)

[Piedone]

Fixes #11560.

This contribution is sponsored by the City of Santa Monica.

[Skrypt]

Ok, I need to review both of these first :

https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl-query-string-query.html
https://lucene.apache.org/core/2_9_4/queryparsersyntax.html

Need to see if the first one is equivalent or not. We need to try to follow ElasticSearch documentation/implementation.

Else, good work. 😄

[Piedone]

While I didn't know about it up until now, this is pretty much a simplified Query string query indeed.

Thanks :).

[Piedone]

Updated according to what was discussed under the issue.

[Skrypt]

All good to me. We should take a second look at the MultiFieldParser later on if it is required but I believe that the SimpleQueryStringQuery should cover that use case.