Start adding explicit reverse zones.

These should make it possible to define extra things for reverse zones. For
example the autodomain will work differently for reverse-zones.
Have automatic reverse domains

Grab the ipaddresses from the given autodomain and add them to the ips.
The autodomain can be a different match then the whole domain (for example
autodomain=10.110.30 while domain is 10.110).
Merge branch 'add_reverse_zones'