Boost search result title matches

Summary: Ref T6740. When a query matches a document title, boost results.

Test Plan:

• Searched for button bar.
• Before:

{F2019463}

• After:

{F2019470}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T6740

Differential Revision: https://secure.phabricator.com/D16945