DRAFT: implement DNS

todo:

• add dns server for private net (dnsmasq seems like the best option)
• debug why avahi doesn't seem to be responding on the same box with avahi-resolve
  • reflector=yes broke avahi resolving, it's not really necessary for valve-infra, so it has been disabled (the default for avahi-daemon)
• use a different domain than farm... .farm is actually a valid TLD, so upstream resolvers are not going to return NXDOMAIN, which seems to break mDNS...
  • .local seems good enough for now