Site plugins used to be used for things like kibana and marvel, but
there is no longer a need since kibana (and marvel as a kibana plugin)
uses node.js. This change removes site plugins, as well as the flag for
jvm plugins. Now all plugins are jvm plugins.
* Added percolator field mapper that extracts the query terms and indexes these terms with the percolator query.
* At percolate time these extracted terms are used to query percolator queries that are like to be evaluated. This can significantly cut down the time it takes to percolate. Whereas before all percolator queries were evaluated if they matches with the document being percolated.
* Changes made to percolator queries are no longer immediately visible, a refresh needs to happen before the changes are visible.
* By default the percolate api only returns upto 10 matches instead of returning all matching percolator queries.
* Made percolate more modular, so that it is easier to add unit tests.
* Added unit tests for the percolator.
Closes#12664Closes#13646
Ryan Ernst
Martijn van Groningen
Simon Willnauer
Adrien Grand
Simon Willnauer
Jack Conradson
Robert Muir