Deprecate the 'restart' daemon option (obsolete since docker 1.2.0).

I just found out that the `--restart` daemon option has been obsoleted in [docker 1.2.0](http://blog.docker.com/2014/08/announcing-docker-1-2-0/). The option is no longer documented and even if its presence won't prevent the docker daemon to start, it will be ignored. The container restart is now done with explicit [restart policies](http://docs.docker.com/reference/commandline/cli/#restart-policies).

This PR deprecates the attribute (which we can keep for now, no harm); we should remove it with version 1.0.0 of the cookbook.