Conpherence - make timestamps in durable column link to full message in conpherence

Summary: Ref T7757. This diff made me realize that PhabricatorTransactionView is only used in Conpherence, as well as that ConpherenceTransactionView is more like a rendering class with a few static methods. Going to take a diff after this to clean all that up.

Test Plan: opened up durable column, clicked on timestamp, voila!

Reviewers: chad, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T7757

Differential Revision: https://secure.phabricator.com/D12409