Add and validate namespace to pod, service, replication controller objects

Next iteration in delivering code against the integrated namespaces proposal, the PR adds the following:

1. Add Namespace to Pod, Service, ReplicationController objects
2. Enforces Namespace is set prior to persistence
3. Enforces context.Namespace on create and update operations matches resource.Namespace

Feedback welcome.

Ok is false when there is no namespace on the context.
Modified a test case to demonstrate the behavior.
I do not think we need to log anything as the calling code returns with an appropriate error to the client that the namespace of the request does not match the namespace on the provided resource.