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.

Why the long name?  OnCreateOrUpdate doesn't seem to add much value, to me.