Add a "--force" flag to bin/auth revoke

Summary: Ref T13043. I'd like to replace the manual credential revocation in the Phacility export workflow with shared code in bin/auth revoke, but we need it to run non-interactively. Add a --force flag purely to make our lives easier.

Test Plan: Ran bin/auth revoke --everywhere ... with and without --force. Got prompted without, got total annihilation with.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13043

Differential Revision: https://secure.phabricator.com/D18895