R1:188c21ae0887

Improve rendering of Conpherence fulltext search results

Summary:
Ref T3165. This:

- Fixes a bug with overlapping matches.
- Makes the UI a little less hideous (and more standard).
- Links comments into the chat history view.

Test Plan: {F396749}

Reviewers: chad, btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T3165

Differential Revision: https://secure.phabricator.com/D12777