By Ewan Murray The traditional English football curtain-raiser takes place this Saturday when Premier League champions Manchester City face FA Cup winners Manchester United in the Community Shield. The local rivals will go head-to-head in what is essentially a glorified pre-season friendly but there is still a piece of silverware and bragging rights on the line for the two Manchester sides. For City, there is extra motivation after they were beaten by the Red Devils in last season’s FA Cup final. Both sides have endured difficult pre-season periods heading to the capital. City travelled to the…