Design of the VectorSpace

Some notes:

• Having a common base class is at odds with inheriting from IndexableContainerBase. We’d have to template VectorSpace on the derived class to have IndexableContainerBase implement it.

  • CRTP for VectorSpace is fine if we never need a VectorSpace object. Would we want a property type like: BraKet<VectorSpace, Operator, VectorSpace> vs say BraKet<AOs, Operator, AOs>? The former is useful for avoiding a combinatorial explosion in property types, e.g. BraKet<MOs, Operator, AOs> and BraKet<AOs, Operator, MOs>.