R1:42b1c73f411f

Allow CC's/Auditors added to audits

Test Plan:
Added CC's/Auditors, clicked the form elements, and saw correct
behaviour. Verified that metadata was present in the detail table.

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, epriestley, 20after4, Koolvin

Maniphest Tasks: T904

Differential Revision: https://secure.phabricator.com/D2002