Presets for Models (NODDI, SANDI, ..)

In the UI, we can add a dropdown button (https://docs.bokeh.org/en/latest/docs/user_guide/interaction/widgets.html#dropdown) next to the "number of compartments" selector. When pressed this button will allow the user to choose a multi-compartment model. The number of compartments, compartment types, and microstructural parameters are then automatically updated.

To support this we make the model.compartments property writable as well as readable. This would allow to update the multi-compartment model in the user interface by setting model.compartments = [list of compartments...].