Add support for container networking config
Add support for container networking config

To modify a container's networking config, set its
"networking_config" key to a docker-py NetworkingConfig dictionary.

E.g. docrane would pick up the following config:

    etcdctl set /docrane/example_containter/networking_config \
      '{"EndpointsConfig": {"named_network": None}'

and ensure that the container started connected to the network
"named_network" with the default configuration.

CloudBrewery/docrane