Last season, Shaw Festival ended its long trip to Narnia after four shows, and none too soon. After a rousing start, the children’s series of shows became increasingly muddled and uninspired. Which made the addition of “The Wind in the Willows” such a welcome addition to this season. It could launch a new series for Shaw, based on the classic British children’s stories by Kenneth Grahame about forest critters and the very adult, very human problems they face.