Modularize Owners package transactions
Summary: Converts Owners package transactions to modular transactions.
Test Plan:
- created a new package
- edited all simple properties from the web ui
- checked that project and user owners were added as reviewers appropriately to new diffs
- inspected the change details for various types of path add / remove / update / reorder changes
Reviewers: epriestley, Blessed Reviewers
Reviewed By: epriestley, Blessed Reviewers
Subscribers: Korvin, epriestley
Differential Revision: https://secure.phabricator.com/D16651