(GREAT BARRINGTON, Mass.) – Folksingers old and new, including Tom Paxton, Maria Muldaur, Tom Rush, Lucy Kaplansky, John Gorka, Vance Gilbert, Dan Bern, the Nields, and Tom Chapin, will perform in this summer’s Troubadour Series at the Guthrie Center in Great Barrington, a season marking the 100th anniversary of the birth of the center’s namesake…