Add --registry-append and --registry-replace qualifier to docker daemon

    These options setup a search list of registries from which to pull images.

    Registries will be searched in reverse order.

    --registry-append will allow you to add additional registries to docker.io to
    pull images from.

    For example

    --registry-append="foo.com/registry,bar.com/registry"

    Would cause a
    docker pull myapp

    to search
    bar.com/registry/myapp
    foo.com/registry/myapp
    docker.io.../myapp

    This would allow companies and vendors to specify registries which contain
    content that the companies will not allowed to be stored at docker.io

    --registry-replace="foo.com/registry,bar.com/registry"
    Would do the same, but not search the docker.io registry.

    This would allow a customer to control which sites that images can be pulled from.

    Docker-DCO-1.1-Signed-off-by: Daniel Walsh <dwalsh@redhat.com> (github: rhatdan)

Docker-DCO-1.1-Signed-off-by: Dan Walsh <dwalsh@redhat.com> (github: rhatdan)

Conflicts:
	docker/docker.go
	server/server.go