Tracking issue: Packages/extensions

[daemontus]

I'll try to keep ideas/discussion about packages in this thread.

[daemontus]

SBase

Currently, SBase implicitly assumes that everything will use the core SBML namespace. For packages, this isn't really going to work. One possible way to fix this is to declare a Namespace trait (or Package?), and then make SBase generic with types implementing this trait. That way, we can say that Model implements SBase<Core> while QualModel implements SBase<Qual> and so on. Of course, in this scenario, QualModel can be still cast to Model. We'll need to think about how this affects the attributes (which can either use the package namespace, or the default namespace, either is fine).