YOU can't cod God, as Sean O'Casey once wrote, and nor can you fool The Irish Times with a blue Babygro. The Abbey has been wall papering Ireland with a publicity picture of a baby, which purports, we infer, to be the young Ernest from Wilde's The Importance Of Being Earnest - and is, in fact, a girl. Now, that's one of the few twists Wilde didn't manage to get into the plot of his great comedy, which opened last night at the Abbey.