Replace NamedType with strong_type

[PatrickKa]

I just found out that NamedTypes cannot be used as non-type template parameters, because they are not structural, because they hold the underlying value as a private member variable. Fortunately, there is another great library called strong_type which we can use instead. It even provides a modifier strong::affine_point<D> which I find super convenient.

Also, remove the debug_assert library, since it was required only by NamedType.