MetaMTA - add (basic) application emails and deploy to Maniphest

Summary: Ref T5952, T3404. This lays the basic plumbing for how this will work, all the way to deploying on Maniphest. Aside from what is mentioned on T5952, I think page(s) on editing application emails could use a little more helpful text about what's going on, similar to how the config page that's getting deprecated works.

Test Plan: ran migration and noted my create email address migrated successfully. used bin/mail to make a task. added another email and used bin/mail to make a task. deleted an email. edited an email. invoked various error states and they all looked good.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T3404, T5952

Differential Revision: https://secure.phabricator.com/D11418

src/applications/base/PhabricatorApplication.php

@@ -4,6 +4,7 @@
  * @task  info  Application Information
  * @task  ui    UI Integration
  * @task  uri   URI Routing
+ * @task  mail  Email integration
  * @task  fact  Fact Integration
  * @task  meta  Application Management
  */
@@ -193,6 +194,22 @@ abstract class PhabricatorApplication implements PhabricatorPolicyInterface {
   }
 
 
+/* -(  Email Integration  )-------------------------------------------------- */
+
+
+  public function supportsEmailIntegration() {
+    return false;
+  }
+
+  protected function getInboundEmailSupportLink() {
+    return PhabricatorEnv::getDocLink('Configuring Inbound Email');
+  }
+
+  public function getAppEmailBlurb() {
+    throw new Exception('Not Implemented.');
+  }
+
+
 /* -(  Fact Integration  )--------------------------------------------------- */