As described in our ROADMAP.md, introduce new Swarm management commands
to call to the corresponding API endpoints.
This PR is fully backward compatible (joining a Swarm is an optional
feature of the Engine, and existing commands are not impacted).
Signed-off-by: Daniel Nephin <dnephin@docker.com>
Signed-off-by: Victor Vieux <vieux@docker.com>
Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>
