Engine: new command 'kill' sends a signal to a running container
Hack: use new 'kill' command in integration tests
gofmt
Engine: port 'kill' to the new integer status.
update docker push to use [====>    ]
revert 'firstErr'
Merge pull request #2735 from shykes/engine-job-kill

New engine command: 'kill'
Merge pull request #3153 from vieux/improve_docker_push_display

Update docker push to use new display