WASHINGTON (Reuters) - Two years after a shooting that left her severely wounded, former U.S. Representative Gabrielle Giffords of Arizona is launching a group aimed at curbing gun violence and challenging the political clout of the well-funded gun lobby. Giffords, herself a gun owner, is starting the effort called Americans for Responsible Solutions with her husband, former astronaut Mark Kelly, after a string of recent mass shootings. "Enough," the former congresswoman told ABC in an interview aired on Tuesday, calling for common-sense measures to reduce violence. ...