R1:3a17220ce3da

T7827: Boost Elasticsearch results on title match.

Summary: If match is found on document title, boost result.

Test Plan:
- Setup phabricator with elasticsearch.
- Index documents with `bin/search index --all`
- Use search and expect query matching titles appear on the top of results list.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: WikiChad, Korvin, epriestley

Maniphest Tasks: T7827

Differential Revision: https://secure.phabricator.com/D12432