Make function arity missmatch exception more informative

[mschoeb]

If we call a function with the wrong amount of arguments it just says “Entered function name and arity doesn't match a defined function signature: "abs" called with 2 parameters.” It would be nice if it were maybe something like “expected 1 but got 2 arguments”

In addition, if some arity is not yet implemented then we could catch that and write that, like matches with arity 3 is not yet implemented. This could also be a good way to keep track which functions are already implemented and which are still missing