Phriction - start the move towards transactions and an editor

Summary:
This implements as little as possible to stick a working transactions + editor codepath in the basic create / edit flow. Aside from the transaction tables, this also required adding a mailKey to a phrictionDocument.

Future work would include adding more transactions types for things like "move" and all the pertinent support. Even future work is to add things like policies which will work easily in the transaction framework. Ref T4029.

Test Plan:
 - made a wiki doc
 - edit a wiki doc
 - had someone subscribe to a wiki doc and edited it

For all three, the edits worked, a reasonable email was sent out, and feed stories were generated.

 - made a wiki doc at a /location/like/this

document "stubs" were made as expected in /location and /location/like

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: chad, Korvin, epriestley

Maniphest Tasks: T4029

Differential Revision: https://secure.phabricator.com/D10756