Allow users to manage package dominion rules

Summary: Ref T10939. This adds UI, transactions, etc, to adjust dominion rules.

Test Plan:

• Read documentation.
• Changed dominion rules.
• Created packages on / ("A") and /x ("B") with "Auto Review: Review".
• Touched /x.
• Verified that A and B were added with strong dominion.
• Verified that only B was added when A was set to weak dominion.
• Viewed file in Diffusion, saw correct ownership with strong/weak dominion rules.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10939

Differential Revision: https://secure.phabricator.com/D15936