Remove 'full-display' setting from Conpherence, spruce up search results

Summary: This removes 'full-display', 'minimal-display' from Conpherence, which I recall was because we had 2 UIs for column and regular chat. I'm also tossing in slightly nicer search results, with a link to the actual message and the full date shown for context.

Test Plan: Post a message in mobile, tablet, full conpherence, and in durable column. Clean up UI in durable column. Do a search in Full UI, click on result date, get taken to the message... usually. My test data is a little wonky, but I think this works most of the time.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Differential Revision: https://secure.phabricator.com/D16710