Scheduler plugin v1

Note that this depends on two things that apiserver doesn't do yet, which I'll fix in future PRs.

(those things being do something when bindings are written, and watch minions)
Also, I think there's a case with etcd during a watch where you can get a 401 if a snapshot gets generated (or has been generated) and the version is now longer available.  I think in that case we need to reset the resource version to 0 and start the watch again to resync the full cache (which we would need to clear to make sure we don't have stragglers).