Put its contents in it and then use them from there instead of importing them
all over the rest of the code.

... so Grafana shows us names instead of VPN IP addresses.

Avoiding catastrophy: It's all about minimizing cognitive overhead.

- Add node exporter to nodes
- Make the old nixpkgs 19.09 node exporter work (amend config)
- Fix a typo (??) and exclude monitoringvpn in network traffic graphs to prevent double counting

... leave some coding fun for later!