Sherman Cymru, CardiffSophie Melville is superb in this reworked version of the myth that follows a disaffected young woman kicking hard against a bleak worldIf you take a slight detour on the walk from Cardiff train station to the Sherman theatre, you can go and see the statue of Aneurin Bevan, founder of the National Health Service. It's not much to look at, and Cardiff's seagulls have been crapping all over it, bu…