Summary:
Migrate to `PhabricatorApplicationTransactions` (`ReleephRequestTransactions` applied by `ReleephRequestTransactionalEditor`, instead of `ReleephRequestEvents` created by `ReleephRequestEditor`) and migrate all the old events into transactions. Email is supported in the standard way (no more `ReleephRequestMail`) as well.
This also collapses the Releeph request create and edit controllers into one class, as well as breaking everyone's subject-based mail rules by standardising them (but which should be more easily filtered by looking at headers.)
Test Plan:
* Make requests, then pick them.
* Pick and revert the same request so that discovery happens way after `arc` has told Releeph about what's been happening.
* Try to pick something that fails to pick in a project with pick instructions (and see the instructions are in the email.)
* Load all of FB's Releeph data into my DB and run the `storage upgrade` script.
* Request a commit via the "action" in a Differential revision.
Reviewers: epriestley
Reviewed By: epriestley
CC: epriestley, aran, Korvin, wez
Maniphest Tasks: T3092, T2720
Differential Revision: https://secure.phabricator.com/D5868
