hotplug script to dynamically configure the local DNS (dnsmasq) to redirect game content servers to a LAN cache. Definitive list dynamically obtained from https://github.com/uklans/cache-domains.
Configuration file follows the same [syntax as the upsteam file](https://github.com/uklans/cache-domains/blob/master/scripts/config.example.json). The key for each `cache_domain` member matches the name of one of the `.txt` files in the [upstream root directory](https://github.com/uklans/cache-domains/blob/master/), except for the `default` key which matches the all the unreferenced `.txt` files. The value of each `cache_domain` member maps to one of the keys of the `ips` members, Thus mapping a cached domain to a list of IP addresses/LAN cache server.
`/usr/bin/cache-domains configure` will configure the local DNS (dnsmasq) to redirect the configured cache domains. `/usr/bin/cache-domains cleanup` will cleanup redirection. The hotplug script calls `/usr/bin/cache-domains configure` when the WAN interface is brought up.