generate changeset from the zone sign
After generating the new NSEC3 tree, some alternative to zone diff should be called to create a basic changeset. Any added/removed RRSETs can be then added directly into the changeset.
[x] updating NSEC3 tree
[x] updating NSEC records
[x] updating RRSIGs
[x] updating SOA if there are changes
[x] generating RRSIGs for records affected by NSEC chain generation (entries not in zone, but in changeset)
[x] generating RRSIGs for SOA