Add a "status report"

[lovesegfault]

Currently it's really hard to understand at then end of a large deployment what worked and what didn't, as the logs from different nodes tend to bury each other.

It would be great for at the end of the deployment process for there to be a "status report" of sorts that gave you a summary of overall status of the deployment.

[bqv]

As discussed on IRC, it would be nice if this was machine-readable (e.g. json) so it can fit into further pipelines