Export metric with fail2ban server and exporter versions

Export a new metric with the fail2ban server version and the exporter version. Since metrics are all numeric, export the version string as the value of a label (and set the value to 1).

Something like this:

f2b_version{fail2ban="7.8.9",exporter="0.3.0"} 1

To collect the fail2ban server version, use the version command (protocol.py)