Conpherence - add support for linking directly to messages regardless of age of message

Summary: Fixes T7757. Since anchor links can't be processed server side, we have to detect the message is old in javascript, then re-loaded the page. This opens up a new corner case where we have to paginate in newer messages, so this also adds support for that.

Test Plan:

• set main query limit to 8 and then visited ZXX#YYY. noted a second quick load of YYY, that YYY ended up highlighted and scrolled to.
• used "show newer messages" and "show older messages" successfully, taking care to make sure transaction ids were all correct with no off by one errors, etc.
• opened and closed durable column to make sure that still works too

Reviewers: chad, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7757

Differential Revision: https://secure.phabricator.com/D12633