Add NXQL HINT syntax to enable Elasticsearch index selection

-- Use an explicit ES field
SELECT * FROM Document WHERE /*+ES: INDEX(dc:title.ngram) */ dc:title = 'foo'

-- Use fulltext search on explicit list of ES fields, here boosting dc;title
SELECT * FROM Document WHERE /*+ES: INDEX(dc:title.fulltext^3,dc:description.fulltext) */ ecm:fulltext = 'foo'

-- Use ES operators not present in NXQL
SELECT * FROM Document WHERE /*+ES: OPERATOR(regex) */ dc:title = 's.*y'
SELECT * FROM Document WHERE /*+ES: OPERATOR(fuzzy) */ dc:title = 'zorkspaces'
SELECT * FROM Document WHERE /*+ES: OPERATOR(common) */ dc:title = 'this is bonsai cool'

-- Use ES query_string on multiple fields using a fulltext analyzer
SELECT * FROM Document WHERE /*+ES: INDEX(dc:title.fulltext,dc:description.fulltext) ANALYZER(fulltext) OPERATOR(query_string) */ dc:title = 'this AND that OR thus'