Add initial lifecycle and hooks into kubelet.

@lavalamp I was referring to hook output back to the user, I was assuming that as a client if I want to see hook results I'd need to be able to identify the pod that specified it, but that I probably want hook info to be historically available (it's more like log results than snapshot info).  So I was assuming that this lived somewhere between the "this died and got restarted" restart info of Dawn's item and the "how do I store, ship, aggregate, and search/view logs for a particular pod" work.  Didn't seem like it fits on either extreme.