From "Romeo and Juliet" to "Love Story," the tale of youngsters who fall in love, only to see death and a search for meaning in it all is so often told that it seems to have become almost a cliche of itself. But when that story gets mixed with history and put into the hands of a small coterie of very creative people, the story creates the kind of theatrical magic that comes only on occasion. That's what happened when "Amelia" opened Saturday night.