Interaction between dynamic parameters and watching

I don't know when this might come up in a real application, but I don't think the watching mechanism is currently hooked up to work with dynamic parameters (e.g numbergen).

If I remember correctly, dynamic generates values every time you inspect a parameter (i.e `__getattr__`) while watch checks for when the parameter is explicitly changed. I haven't checked, but I don't think that watch is triggered every time a dynamic value is generated (which to be consistent, I think it should)