Zebra: support no auth in web UI

The web UI should not do any authentication when posting a job in the Zebra test environment — the authentication has already been done when you login and the browser will thus have the necessary cookies set already.

This pull requests adds support for this. You can pass `--no-ui-auth` to `zpm deploy` and the auto-generated UI wiil then not contain a username/password pair. It will simply contain the Swift URL that is needed for posting the ZeroVM jobs.

The lack of authentication is signaled to the JavaScript ZwiftClient by setting the authentication version to 0. It is only the JavaScript client that supports this form of "authentication" — the Python version always need authentication since it is running on the user's machine and needs to login in order to upload the files.