Adding setter types

Adds type to top-level accessors and class accessors.

Requires that setter have exactly one `SimpleFormalParameter` or shows nothing.

Contributes to #2613.

@devoncarew 
We could just show the first one. I'm assuming the user's file will display an error at the source location. The outline view can do a best effort to display something for bad code. In this case - two args to a setter - we can just display the first arg type.