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.
This indentation fix is good in principle, but I don't think we should fix it in only this file. All files are like this, so we should fix them together. Just fixing one may lead to search-and-replace problems later on.