Allow datetime inputs to be optional
Summary:
Fixes T3279. For ApplicationSearch (and in some other cases) I'd like users to be able to provide an optional date. This isn't currently possible.
Add a checkbox which disables or enables the input.
Test Plan: Used UIExample to enter dates. Used Calendar to enter dates.
Reviewers: chad, btrahan
Reviewed By: chad
CC: aran
Maniphest Tasks: T3279
Differential Revision: https://secure.phabricator.com/D6082