It is a gorgeous day in Sacramento as I stroll through the crowd of revelers celebrating ice cream shop Gunther’s 70th anniversary. Mayor Kevin Johnson stops to say hello to me, and then I am stopped by a handsome, well-dressed young man in jeans and a button-down dress shirt with the sleeves rolled up. He's wearing trendy aviator sunglasses and is surrounded by a large group of young people in Marcel 2010 T-shirts. “Are you Erin," he asks. "I’m Marcel and I believe we have an interview.”   Marcel Weiland is not the typical politician -- he's young and never has been elected to a position. He's quick to remind me that he will turn 20 in November, but seems older. While many of his friend