Emulate dnsmasq tag feature, or allow per host DNS announce override

[philjohn]

Dnsmasq has a great feature where you can setup a tag, e.g. for children's devices, with separate DNS servers to announce (in this case OpenDNS filtered) and then have that tag assigned in various host settings in /etc/config/dhcp

This allows a certain amount of "parental control" functionality, in addition to setting time limits via the firewall.

It would be fantastic if a similar functionality was provided in odhcpd. Failing a tag feature, the ability to set per-host DNS announce overrides via /etc/config/dhcp would be a good second.

There are possible workarounds with redirecting all DNS traffic for certain hosts to somewhere else, but setting that up in the firewall could get cumbersome.