“While it took place just a generation or two ago, the fertile tumult of the early years of the Off Off Broadway theater movement seems almost as distant. Wading through the tricked-out strollers clogging the streets of Greenwich Village today, it is hard to conceive that not so long ago — well, O.K., getting on toward 50 years now — a scrappy, determined bunch of young artists ignited a vibrant new era in theater by staging plays in local coffeehouses, churches and other commandeered spaces.”