Convert Calendar Events to use RRULE frequency constants in various other places
Summary:
Ref T10747.
- Store recurrence as RRULEs internally.
- Use RRULE constants.
- Migrate existing rules to RRULEs.
Test Plan: Ran migration, nothing seemed broken?
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T10747
Differential Revision: https://secure.phabricator.com/D16670