Add supervisor daemon and ssh

Moved common configurations outside of this PR: 
https://github.com/ifunsoftware/c3-next-docker/pull/1

## Original description:

Inspired by this:
http://docs.docker.com/examples/running_ssh_service/

and this:
https://docs.docker.com/examples/running_riak_service/

Makes container easier extensible (Just add a new background service to supervisor config: C3 web, etc...)