NXQL query with LIMIT or OFFSET should be considered as invalid

LIMIT and OFFSET are not supported by the [NXQL|doc.nuxeo.com/display/NXDOC/NXQL] syntax.
Nevertheless, a query that uses LIMIT or OFFSET is valid.
The risk is to wrongly think that LIMIT is taken into account.

We may want to support LIMIT/OFFSET but in the meantime, we should at least add a warning trace that they are ignored.