Also: Jam on The Brandywine, Sept. 20 By Denny Dyroff, Staff Writer, The Times For more than three decades, the Chester County Restaurant Festival (Gay Street and downtown area, West Chester, 610-436-9010, http://chestercountyrestaurantfestival.com) has been treating visitors with the opportunity to sample a wide variety of gourmet treats. This year, the free festival, which will be held on September...