Add support for machine readable formatters

Add support for machine readable formatters based on https://review.openstack.org/#/c/287536/. This will required an update to cliff version requirement.

Many OSC commands (need to compile a detailed list) format dicts and lists to improve human readability when creating, showing and/or listing a resource. This formatting needs to take into consideration machine readability for output such as JSON or YAML.

Related discussion on this blueprint:
http://eavesdrop.openstack.org/meetings/openstackclient/2016/openstackclient.2016-03-03-19.00.log.html