How should users specify an ensemble?

[k-doering-NOAA]

@msupernaw and I discussed a few weeks back that it would be helpful to think of a different way to specify the ensemble that should be run from a Stock Synthesis model.

@msupernaw not sure if the changes recently pushed pertained to this?

Some ideas from previous examples:

• users could call an R function and pass in some arguements to it (e.g., https://github.com/nmfs-fish-tools/SSMSE#create-the-operating-models-oms)
• users construct a list of datafames (or lists, as needed) (e.g., https://github.com/nmfs-fish-tools/SSMSE#add-observation-error-through-sampling-from-om)

It would be great to add s3 or s4 objects to provide more structure to the ensemble object, though.

[msupernaw]

@k-doering-NOAA I thought we could define the ensemble objects using the s4 objects we already have. I've added some global lists to house them. We can use a large amount of Bai's code to define data and the model specification. Bai already has functions to run SS, MAS, ASAP, AMAK, and BAM. It's just a matter of refactoring a few things and putting it all together and extending from there!