Is ganja coming to a neighborhood near you? As soon as Bay State voters legalized medical marijuana last month, area cities and towns began pondering whether they could restrict pot dispensaries within their boundaries. On another health front, parents, physicians, and coaches debated whether any  equipment can protect young athletes against head injuries (the short answer: maybe). And communities like Westborough argued over large ­solar-panel arrays, trying to balance “go green” enthusiasm with aesthetic concerns.