convert openvpnzone into  authority and watch status file
convert openvpnzone into  authority and watch status file

Convert openvpnzone module from pyzonefile into normal python module which
implements a new twisted.names.authority that parses a openvpn status file.

Extend authority to listen per inotify for file changes. A rereading can be
enforced via the USR1 signal.

The serial number for the zones are generated from the modification time as
unix timestamp.

mswart/openvpn2dns,mswart/openvpn2dns