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
