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)
I was wondering if there is any case where this would be invoked.  I'm not positive, but if an etcd leader election happens and the term gets rolled back, the next index could be lower, BUT it would be the index we should use.  If we stayed at the higher version we would miss updates.