Mark's networking code

As cleaned up by @ediosyncratic using git filter-branch (among other dangerous tools).
Includes several fixups from later in the branch, but I may have missed some.
Compiled locally and passes all unit and acceptance tests.  Let's see how it fares more widely ...

I suspect reviewing the gross diff is easiest, as there are (even after squashing out a few) quite a lot of changes of mind along the way.  Also: 106 commits.
Does this change the format of IPV6 hard classes from ``aaaa__1`` to ``ipv6_aaaa__1``? Not necessarily a bad thing, it is more properly namespaced, but we may need to keep the original around for existing policies. @markburgess?