* Remove gateway and netmask from dhcp section

  * Remove gateway and netmask from dhcp section
  * Add leasetime to dhcp section, crank it down from default 1d to 1h
  * Get rid of bogus 2.181.18.in-addr.arpa authoritative zone; that's
    not our subnet, and we act authoritative for reverse addresses that
    are in our database anyway.
  * Remove symbolic -internal names of hosts since they're not actually
    defined anywhere, and populate the actual internal IPs of the hosts,
    so migrations may be possible.
  * Remove old sipb-noc address from monitoring and noc sections.