Network.__new__'s required params argument breaks torch compatibility

[elcorto]

When this is a required arg, it breaks torch.save() and torch.load(). But more importantly, it also breaks code that does copy.deepcopy(model).

One option is to make it an optional keyword arg which defaults to None. When torch.load() de-serializes an object, it will first call __new__ to create a class, then create an instance and populate this with data, such that in this case params=None is justified.