Zoneextractor tool

zoneextractor.py helps on the client-side of the new zone
import API. It takes a BIND9 named.conf and writes out or prints a
zonefile for every configured master zone. Said zonefile can then be
curled or otherwise submitted to the zonefile import API.

Change-Id: Ibc15639771da52e678be067ec4474bcbcc2f0865
Merge "Zoneextractor tool"