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.
Can we update this to `PORTAL+NET="10.0.0.0\/16"`. We need to escape the `/` due to the use of sed later on.

Other than this, I'm okay with these changes. We have to rework a bunch of stuff after https://github.com/GoogleCloudPlatform/kubernetes/pull/1532 anyhow.