Refactor dynamic subforms

I would like to have a more uniform solution for viewers with subforms.

This is intended for exploration viewers at first: phase plane, stimuli creators, local connectivity. 

We usually have a field with choices (select field, radio buttons etc) and each time the value changes, we have to display the proper subform. We do a request to the server in order to receive the new subform. We need events on every subform's field change. Those need to be added on the client side each time the subform changes. Plus, most of the time, we need to generate a redraw.

Started some work on a local branch and I would like to finalize it in the next sprint.