Investigate IPv6 support

[Athanasius]

Once other code cleanup is finished (i.e. ensuring all services log proper IP addresses, not 127.0.0.1 due to reverse proxying) we should investigate enabling IPv6 connectivity for both uploads to the Gateway and listening on the Relay.

The current host has IPv6 addresses and this would introduce an extra wrinkle to changing servers in the future, but that's a problem for just that, the future.