Provide IPFire specific items for the Zabbix server to monitor:
- ipfire.net.gateway.pingtime: Internet Line Quality
- ipfire.net.gateway.ping: Internet connection
- ipfire.net.fw.hits.raw: JSON formatted list of Firewall hits/chain
- ipfire.dhcpd.clients: Number of active DHCP leases
- ipfire.captive.clients: Number of Captive Portal clients
Signed-off-by: Robin Roevens <robin.roevens@disroot.org>