Programmatic way to specify parameter space

[raar1]

During the hackathon it became apparent that the current way of specifying parameter space (by providing a params dict in the input json file) is problematic for approaches such as @jlakhlili 's PCE case in which a potentially large number of varying parameters may be needed. This can happen e.g. when you need a large vector of parameters.

The most intuitive/logical approach in such cases would be to programmatically construct the params dictionary during the user script.

I propose that we add functionality to Campaign to allow the params stuff to be built in-script.

[raar1]

This has been essentially addressed in the recent refactor. Apps are now added programatically, and are passed the params block in-script.