Have HTML mails return to and cc lines
Summary: Fixes T6525, adds cc and tos to html emails
Test Plan: send html and plain emails, see new stuff
Reviewers: btrahan, epriestley
Reviewed By: epriestley
Subscribers: Korvin, epriestley
Maniphest Tasks: T6525
Differential Revision: https://secure.phabricator.com/D10857