Transactions - make edit transactions that are grouped work nicely

Summary: ...the key is to move a layer lower and beam down the updated comment. There is a wee bit of Javascript gymnastics going on here. Fixes T4608.

Test Plan: made a comment + resolve. clicked edit and made changes. noted transaction updated correctly and "history" link worked. edited again to a deletion and noted the "this is deleted" looked right and history link still worked

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin, chad

Maniphest Tasks: T4608

Differential Revision: https://secure.phabricator.com/D8702