run: option to specify resource actions upon at the initiation and upon completion of the run in --follow mode

[yarikoptic]

AWS EC2 time is not cheap, we should make it possible to "fire and forget" a computation without monitoring the progress to just shut it down to not incur charges when it is already idling.

Ideally reproman run -r mylarge-ec2 would start mylarge-ec2 first, do all the run needs, fetch the results and stop the resource upon completion. So may be it could be as simple as a predefined list of actions to do on the resource, e.g. --resource-actions={start,stop-after,delete-after,email-after}?

[kyleam]

gh-479 addressed this aside from the "email-after" suggestion.