(NORTH ADAMS, Mass.) – Building on the success of last year’s first foray into bluegrass, MASS MoCA has announced the dates, line-up, and discounted early-bird pass price for the second annual FreshGrass Festival, which will be held September 21-23, 2012, and will be headlined by David Grisman Bluegrass Experience, Trampled By Turtles, and Carolina Chocolate…