`expose` and `unexpose` commands are now fully functionnal using the
ambassador pattern. This has the advantage to be a 100% docker solution
and to not have to restart the service container. Multiple ports are
exposed when service specify them.
`start` and `stop` commands have been made more robust. When calling
`start` or `stop` on an already started (or stopped) service, an error
will be printed out instead of issuing failing commands.
Exposed services will still be exposed after a `restart`. Also the
service containers (and ambassador containers) will start automatically
when docker boot up.
