A look at five must-see art exhibitions in Paris this spring, from French artist Abraham Poincheval’s eccentric Oeuf (“Egg”) at the Palais de Tokyo to the thought-provoking “Us and Them” at the Musée de l’Homme. Oeuf (“Egg”) It may be too late to see French performance artist Abraham Poincheval entombed inside a giant limestone rock for…