Stuart Spina, a 17-year-old student at Commonwealth School, stood before the MBTA Board of Directors yesterday and told them how to fix some of the most sluggish, inefficient routes. Spina produced a 22-page report that was more detailed than what any pricey consulting firm could pull off. Read it, and you might want him in a major transportation leadership position. He studied multiple bus lines, including the notorious bus 23, which another teenager exposed as......