Expose params to znrnd.models classes as parameter

[jhossbach]

Instead of writing something like network.model_state.params we can add a property to the class for convenience

@property
def params(self):
    return self.model_state.params

This is just a tracker for a future PR until #49 is merged

[KonstiNik]

The idea of the train state is that it includes everything you need for training.
I think it is reasonable to get to the parameters through train state only, because using params as an additional attribute might seem confusing then.
I actually would prefer it how it is right now.

[SamTov]

I don't really mind either way, I would suggest that if you make the param then you need to be absolutely sure that it gets updated automatically when the model state is updated, i.e that it is a pointer, which I do not know off the top of my head. If you can ascertain this and you can make that work nicely then I would say do as you please. The params are fundamental even if the train state goes which for other models it might.