Also: Chadds Ford Art Sale, antiques at Kimberton and more! By Denny Dyroff, Staff Writer, The Times If this weekend’s special event in Kennett Square had a theme song, it would have to be Pharrell Williams’ Grammy-winning hit “Happy.” That’s because March 20 is Happiness Day in Kennett Square. March 20 has been established as the annual International Day of Happiness and all 193 United...