R1:c09e87073311

Prepare event dates for EditEngine/API

Summary:
Ref T9275. Currently, the "Start Date", "End Date", and "Recurrence End Date" transcations take a complex value (AphrontFormDateControlValue) and reduce it to an epoch.

Do this a little earlier, since the API will be much more usable if it just passes in epoch timestamps.

Events also have some logic where they rewrite the from date and to date on the actual object for all day events, then undo the changes later. Specifically, if you have an all-day event…