For 40 years, Eric Jackson has offered up the best of jazz on the WGBH airwaves. He's guided his legion of fans from the swing to the Big Band era, educated generations on bop, avant garde and fusion, and introduced listeners to today’s modern jazz innovators. So what's next for the Dean of Boston Jazz Radio? We reflect on -- and raise a glass to -- four decades of Eric Jackson, who made jazz come alive for Bostonians.