Provide a standalone bin/calendar reload ... workflow for testing/debugging

Summary:
Ref T11801. This makes testing/debugging a little easier.

Also fix some inconsistencies with importAuthorPHID handling -- it should be the import's author PHID in all cases, so we update imported events properly.

Test Plan: Imported a French holiday with bin/calendar reload ....

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T11801

Differential Revision: https://secure.phabricator.com/D16814