Generic types can be called with argument(s) to produce a new type object, and if all types supplied as arguments are concrete, then the result will be a concrete type. The test of a generic type must determine if the entity is an instance of any specialization of the type; and it must also have a `refine` method that takes such an instance and returns its fully-specialized concrete type. It must also have a method `specializesTo` that takes a concrete type and returns whether that concrete type is a specialization of this generic type.
This commit also defines a generic Complex number type, that can have any type as its Component type (including another Complex number, to create e.g. quaternions), and defines the conversion/constructor function `complex`.
Reviewed-on: #21
Co-authored-by: Glen Whitney <glen@studioinfinity.org>
Co-committed-by: Glen Whitney <glen@studioinfinity.org>
