ON THE FACE OF IT, the reinstallation of selected works of art from the Frick Collection in the Breuer building at 875 Madison Avenue provides a refreshing change. After as much as a century in the same setting, masterpieces once embedded in a Gilded Age mansion are now out on their own. Hung on the plain walls of a concrete Brutalist icon, spaced apart from each other, paintings, sculptures, porcelains, two rugs, and some great eighteenth-century French furniture have temporarily jettisoned the ornate wood paneling, lavish curtain window treatments, and decorous fountain courtyard of what was