Allow users to re-accept or re-reject a revision if they have authority over package/project reviewers not yet in the target state

Summary:
To set this up:

• alice accepts a revision.
• Something adds a package or project she has authority over as a reviewer.
• Because alice has already accepted, she can not re-accept, but she should be able to (in order to accept on behalf of the new project or package).

Test Plan:

• Created a revision.
• Accepted as user "dog".
• Added "dog project".
• Re-accepted.
• Could not three-accept.
• Removed "dog project.
• Rejected.
• Added "dog project".
• Re-rejected.
• Could not three-reject.

Reviewers: chad, eadler

Reviewed By: chad, eadler

Differential Revision: https://secure.phabricator.com/D17226