BEIJING — President Trump shook hands with Chinese leader Xi Jinping Wednesday to kick off a historic summit between the world’s two most powerful heads of state. Trump and Xi stood shoulder-to-shoulder outside China’s Great Hall of the People, a massive Communist Party showpiece overlooking Tiananmen Square, during the lavish arrival ceremony .  The handshake marks the seventh face-to-face between Trump and Xi and the pair’s first meeting in China since November 2017.  After greeting each