MetaMTA - more progress towards a mail application

Summary:
Ref T5791. This diff does a few things...

• Adds code to write recipients to edges on save
• Makes Query performance for policy filtering okay-ish
• Adds a Search Engine for PhabricatorMetaMTAMail
• Adds "working" List Controller
  • Inbox and Outbox both work
• Adds stub View Controller

Test Plan: ran ./bin/storage upgrade and saw my inbox and outbox start getting data. played with application and saw new entries in inbox and outbox

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Maniphest Tasks: T5791

Differential Revision: https://secure.phabricator.com/D13397