By THÉRÈSE MARGOLIS     You have a wardrobe of clothes, shoes, jewelry, lipstick colors and nail varnishes. But a wardrobe of skin foundations, with various textures, finishes and coverages? Do you really need a cupboard of different types of base makeups? Dior International Pro Team makeup artist Nicolás Berreteaga says yes. “Your foundation is the … well, foundation of your entire makeup