Fix slave and forward dns zones

[opennetadmin]

currently defining forward zones is broken entirely. A lot of this has to do with the build bind script.

secondly both forward and slave zones only allow for domains with masters that are defined in ONA. I should be able to add a field to dns_domain_servers table that would allow these zones to use a list of IP addresses that were manually added. If this field is provided it will add the value into the list.

This should allow me to mix both entries from ONA and the static list if provided to become a full list of slaves/forwarders in the DNS config.