Remove duplicate config properties for autoritative nameservers

A single property that contains a list should be sufficient to model all
use cases.
Streamline comments

Alignment indentation structure etc.
Sort/fix resource record samples
Streamline comments

Alignment indentation structure etc.
Move BIND integration into separate subdirectory

Now the data under zones define a "pure", service-independent zone
configuration. This would also allow the integration of other DNS server
vendors.
Extend bind configuration to completely describe a nameserver topology