Summary:
Ref T10747. This does double-writes and starts generating/writing CalendarDateTimes.
This greater flexibility is necessary to support the full range of ICS-specifiable events, including "floating" events.
This doesn't do anything yet.
Test Plan: Created and edited events, verified sensible representations of corresponding datetimes appeared in the database.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T10747
Differential Revision: https://secure.phabricator.com/D16661
