Use config sources for Kubelet, switch to podFullName

As discussed in #297 and also a side discussion about abstracting the Kubelet from being directly dependent on etcd, start refactoring config service to decouple sources of config from sync loop and switch from Manifest.ID -> Pod Full Name in the Kubelet.

Simplifies the Kubelet Run() step by requiring configuration to be defined up front, and an update channel passed into the Kubelet.
Understand - since the sync (push full config every x seconds) was moving outside run it no longer felt appropriate to have Run be an "init" style method.  So as a consequence tried to bring everything up a level.