Services v2 (ip-per-service)

DO NOT COMMIT.  Needs test updates and a new e2e test.  Some FIXMEs still.  95% complete.

Add support for IP-per-service behavior.  This creates virtual IP addresses for each service, and uses iptables to route traffic "magically".

The first few commits are relatively independent, and could be extracted to different PRs, if you feel like making me suffer.

See #1107 for background.
Hmmm, wondering how this will be compatible for both definitions of `ssh-to-node`. You can always use something like:

```
ssh-to-node "${test_node}" sh -c "..."
```

Though in Vagrant's case that will do `-c "sh -c \"...\""`, not that there's anything wrong with that though...