Photo It has been a frustrating ten years to be a United fan Since Sir Alex Ferguson left Manchester United in 2013, it has been largely a period of disappointment for the club and its fans. Ten years featuring seven managers, a few highlights, but mainly anger, frustration and even disillusionment. What progress there has been has subsequently turned out to be false dawns. Don’t forget, it was not that long ago that the side were being humbled by Brentford.…