Rename playbook to playbook-pull

Rename playbook to playbook-pull

We'll have to push a lot of our configuration, because it's the only way
we'll be able to use ansible-vault (and thus keep secrets secret).

We still want the pull functionality, so we can use that to bootstrap a
way for ansible to connect to the devices. Likely autossh to a known
server with a reverse tunnel, but that'll come in future commits.