Change all references to the container ID in pkg/kubelet/... to the
strong type defined in pkg/kubelet/container: ContainerID
The motivation for this change is to make the format of the ID
unambiguous, specifically whether or not it includes the runtime
prefix (e.g. "docker://").
Add an experimental network plugin implementation named "cni" that
uses the Container Networking Interface (CNI) specification for
configuring networking for pods.
https://github.com/appc/cni/blob/master/SPEC.md