Add an "Authority" control to Packages to support "Watcher" packages master
Summary: See T13657. An install has "watcher" packages which should not allow owners to "Force Accept" other packages. Test Plan: - Created package A, which I own, on "/", with "Weak" authority. - Created package B, which I do not own, on "/src". - Created a revision which touches "/src" and added package B as a reviewer. - Attempted to accept the revision... - Before patch: permitted to "Force Accept" for package B. - After patch: not allowed to "Force Accept" for package B. - Verified that setting package "A" back to "Strong" authority allows a force-accept for package B. Subscribers: PHID-OPKG-gm6ozazyms6q6i22gyam Differential Revision: https://secure.phabricator.com/D21674