Percolator - Provide ability to not evaluate all queries when requesting N Hits

[gingerwizard]

Currently percolator allows you to control the number of matches with a size parameter. However, it always reports the total number of matches and thus is forced to evaluate all queries irrespective of the size. On larger percolator deployments, the total number of matches is sometimes not required and only the

Request the addition of a total_hits parameter. If true, all queries will be evaluated. If false, all queries will be evaluated only if no size parameter is provided - otherwise Percolator will simply drop out.

Introduces considerations with sorting that need discussion

[gingerwizard]

@martijnvg

[clintongormley]

For consistency, perhaps support the terminate_after parameter instead. See https://www.elastic.co/guide/en/elasticsearch/reference/current/search-request-body.html

[clintongormley]

@martijnvg what do you think?

[martijnvg]

@clintongormley I think supporting terminate_after makes sense.