R1:7ddd570fa535

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