Ddupdate

* Add ddupate-config configuration script.
* Add missing ddupdate.conf.5 manpage
* Static code checkers cleanup
* Documentation updates
* Fix bogus error message in --list-services/addressers.

* Documentation fixes

* Declared as beta state.
* Revise API

* Split old --list command to --list-services and list-addressers
* Split old --options to --address-options and --service-options.
* Incompatible CLI changes
* Documentation fixes.

* Fix start exception on python 3.4/jessie (6).
* Fix unhelpful error messages for bad .netrc (5).
* Documentation fixes.

* Revise and finish ipv6 support (3)
* New option --version, ipv4/ipv6/all addresses switch.
* New ip plugin default-web-ip6, external ipv6 address.
* Update and document proxy usage (4)