Croke Park is never quiet. Even on bleak November midweek mornings, you see people heading through its doors, either to various conferences or functions, or to do the Skyline tour, or to visit the GAA Museum. The latter has been a massive success since it opened its doors for the first time in 1998. Since then, around 4.5 million people have visited the museum. It begs the question, though: why isn’t there a Museum of Irish Sport? Where better to hang Roy Keane’s shirt from the 2002 World Cup – the shirt that was never worn. Think of the possible…