Set up metric collection with prometheus and telegraf as the SNMP proxy.

Each entry in `prometheus_config` should define `name`, `hosts` and optionally `interval`. As above, `hosts` is used as a query filter.

For SNMP the properties `snmp_hosts` and optional `snmp_interval` should define respectively the NetBox query filter and poll interval.

For example:

    {
        "prometheus_config": [
            {
                "name": "classroom",
                "hosts": "role=desktop-computer status=active location=classroom",
                "interval": 300
            }
        ],
        "snmp_hosts": "role=switch name__isw=sw- status=active status=staged status=planned",
        "snmp_interval": 300
    }