Get the status of a simulation group

[Baguage]

Moved from redmine, ticket 6362
Above a certain threshold (#), the status is represented as aggregate stats:

• Number of simulations submitted (in queue)
• Number of simulations running
• Number of simulations finished (successfully) - output received
• Number of simulations failed (error occurred)

Below the threshold, the status for each simulation in the group is returned:

• simulation's id_on_client : status code

If status code == running model, then also include % done.

Probably want an option (a flag in request body, or query parameter) to get individual statuses for all simulations in the group regardless of the threshold.