Maine meets Broadway in “On This Island,” filmmaker Stephanie Slewka's saga of a homegrown musical that helped ease “the civil war of North Haven.” The show: “Islands: The Musical,” which was staged by retired Broadway producer John Wulp on the tiny Penobscot Bay island North Haven with a cast entirely made up of islanders. Ironically, Wulp caused the trouble in the first place when he started a theater program at the island's school that foes claimed distracted from the three “r”s. His goal with “Islands”: “Restore a sense of community.” Sigourney Weaver narrates.