Add a "remove projects" action to Herald
Summary: Fixes T7849. This adds "Remove Projects" to all objects which implement PhabricatorProjectInterface.
- Wrote a rule to remove a project, edited task, saw the project removed.
- Admired entirely reasonable implementation complexity.
Reviewed By: btrahan
Maniphest Tasks: T7849
Differential Revision: https://secure.phabricator.com/D12505