PARIS (Reuters) - A management shake-up at Europe's Airbus accelerated on Tuesday as Nicolas Chamussy was replaced as the head of Space Systems.Airbus said the 51-year-old space engineer would have an unspecified future role, while his job as head of space activities including the company's 50 percent share of the ArianeGroup rocket venture will be taken by Jean-Marc Nasr.The move comes less than four months after Nasr, 57, was named head of Asia-Pacific, responsible for group strategy and..