Added scoring support to percolate api

Scoring support will allow the percolate matches to be sorted, or just assign a scores to percolate matches. Sorting by score can be very useful when millions of matching percolate queries are being returned.

The scoring support hooks in into the percolate query option and adds two new boolean options:
* `sort` - Whether to sort the matches based on the score. This will also include the score for each match. The `size` option is a required option when sorting percolate matches is enabled.
* `score` - Whether to compute the score and include it with each match. This will not sort the matches.

For both new options the `query` option needs to be specified, which is used to produce the scores. The `query` option is normally used to control which percolate queries are evaluated. In order to give meaning to these scores, the recently added `function_score` query in #3423 can be used to wrap the percolate query, this way the scores have meaning.

Closes #3506