Add Room typeahead for Conpherence Search
Summary: Ref T3165. Builds an ngram table for Conpherence Room titles, allowing a tokenizer for searching a subset of rooms.
Test Plan: Say Gabbert in two different rooms, search all, see two rooms returned. Search specific room, see specific result.
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin
Maniphest Tasks: T3165
Differential Revision: https://secure.phabricator.com/D16692