Implement an approval queue

Summary:
  - Add an option for the queue.
  - By default, enable it.
  - Dump new users into the queue.
  - Send admins an email to approve them.

Test Plan:
  - Registered new accounts with queue on and off.
  - As an admin, approved accounts and disabled the queue from email.

Reviewers: btrahan

Reviewed By: btrahan

CC: aran

Differential Revision: https://secure.phabricator.com/D7576

scripts/user/account_admin.php

@@ -181,6 +181,7 @@ $user->openTransaction();
     $editor->createNewUser($user, $email);
   } else {
     if ($verify_email) {
+      $user->setIsEmailVerified(1);
       $verify_email->setIsVerified($set_verified ? 1 : 0);
     }
     $editor->updateUser($user, $verify_email);