If users are on the email to Phabricator, do not send them the Phabricator reply.

Summary: When we receive an email, figure out if any of the other tos and ccs are users. If they are, pass their phids through the stach as "exclude phids" and exclude them from getting the email.

Test Plan: used the various applications (audit, differential, maniphest) and noted emails were sent as expected.

Reviewers: epriestley, vrana

Reviewed By: vrana

CC: aran, Korvin, vrana

Maniphest Tasks: T1676

Differential Revision: https://secure.phabricator.com/D3645