Ability to save out the model builder state in webview to a .py script - for teaching purposes

[acaruana2009]

It would be useful if there was an option to save out the state of the model builder to a .py script (similar to how this can be done in the NIST reflectivity calculators).

This could be kept to quite a limited scope, and we could decide some specific ways we would convert from for example a defined slab in the model builder to what it would look like in code - possibly could add some generic annotations as well if it makes sense.

The main aim of this would purely be for teaching purposes and lower the barrier to entry for scripting.

[bmaranville]

There is a skunkworks script floating around that does this for any model that can currently be built in the refl1d Simple Model Builder. @welbournR has a copy ... but we should integrate it into the server so that users have a button to push.