It may have looked like simple joyriding on a Friday afternoon, but the Parks Dept. employee careening around Battery Park near Whitehall St. yesterday afternoon was actually a man on a mission, i.e. to kill as many birds in the park as possible. Martin Hightower has been a Parks Dept. employee since 2005, but was arrested after 911 started receiving calls about a man driving recklessly on a golf cart at the southern tip of......