Refactor Kubelet config sources for clarity

Create a new "Pod" concept which can identify pods from
many config sources.
Switch the Kubelet to use kubelet/config

Also transfer the Kubelet from using ContainerManifest.ID to source specific
identifiers with namespacing.  Move goroutine behavior out of kubelet/ and
into integration.go and cmd/kubelet/kubelet.go for better isolation.
Merge pull request #356 from smarterclayton/refactor_config_sources

Use config sources for Kubelet, switch to podFullName