The sad ending of James Levine’s tenure as music director of the Boston Symphony Orchestra was of course the biggest local story in classical music this year. His resignation marked the end of a remarkable era of revitalization at the BSO that Levine launched but could not see to fruition. Despite all the Sturm und Drang in Symphony Hall, the city’s wider classical music scene - which is really more like an archipelago of mini-scenes - continued its steady hum.