I should be able to define Signatures for my own Functions

(User Story, To be Fixed , Priority: High, Test Status: No automated tests yet , Reported By Justin du Coeur, )
Functions
Summary: We've added the concept of Signatures and Named Parameters, and those are beginning to work nicely for InternalMethods. But there is no way to do that for user-defined Functions yet.
The problem here is mainly display. In principle, this is easy: Signature should become an encouraged Property on Function. But the format of the Default Value depends on the Type, and we don't yet have a way to link those.