[WIP] Add container command execution proposal

That can be client logic to start with - that's part of what i'm working with dario on is the generic patterns to allow that.

----- Original Message -----
> > +
> > +- forwarding a port from the user's machine to multiple containers
> > +
> > +
> > +## Container specification
> > +
> > +A user must be able to specify the container or containers in which the
> > requested command should run and/or the port forwarding should occur. A
> > container is uniquely identified by the combination of a namespace, a pod
> > name, and a container name.
> > +
> > +Here are possible ways to specify one or more containers:
> > +
> > +1. A reference to exactly 1 container, which requires an exact match on
> > namespace, pod name, and container name
> > +2. A reference to a group of containers, which requires an exact match on
> > namespace, a label selector match for pods, and an exact match on
> > container name
> > +
> > +Question:
> > +
> > +- Would we want to target containers spanning multiple namespaces?
> 
> Would we want to be able to run a command in all pods with label name=foo,
> container=bar, across all namespaces I have access to?
> 
> ---
> Reply to this email directly or view it on GitHub:
> https://github.com/openshift/origin/pull/576/files#r21923540