def apply_link! lnk
            init! lnk.door
            clear_dsts!
            add_dsts *lnk.dsts
            set_link_keys *lnk.keys
        end
def apply_link! lnk
            init! lnk.door
            clear_dsts!
            add_dsts *lnk.dsts
            set_link_keys *lnk.keys
        end
applies the effects of the given Link

 @param [Link] lnk the link to apply effects

 updates @src with Link @src, clears the destination list
 adds the Link destinations to @dsts, sets the @link_keys