Basic Conpherence Search in Thread

Summary: Adds a search bar toggle and results for searching inside a Conpherence Room. The UI of the results itself are not styled yet, and will follow up with another diff.

Test Plan: Go to Conpherence, search for "asdf", get lots of results. Search for nothing, get no change, search for something fictitious, get no threads found (will follow up with search result UI).

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D16697