Copy everything from how the issuer does it.

Just require hostName and domain instead of an extra publicIPv4 option.  Leave
behind a similar option, `publicAddress`, just in case it needs to be
overridden at some point, but stop supplying a value for it anywhere.

The original domain got some state created for it by certbot.  The
certificates are anchored to `payments.privatestorage.io` in the filesystem.
The code handling these domains uses the first domain name in the list to find
the certificates, so make it match the filesystem state.

More flexibility and less dots in config files.
Implements #65.

We might want to merge this before turning on live payment.

Related to privatestorageops#333.

Also put library code in a library directory