Summary:
Ref T2625. Fixes T2812. Implement ApplicationSearch in People.
{F44788}
Test Plan: Made People queries. Used Conduit. Used `@mentions`.
Reviewers: btrahan, chad
Reviewed By: chad
CC: aran
Maniphest Tasks: T2625, T2812
Differential Revision: https://secure.phabricator.com/D6092
