YOU HEARD IT here first—unless you’ve already gotten to the last page of the April issue of House Beautiful. (Hmmm, seems to me I’ve read this before. Anyway. . . ) Gypsophila, baby’s breath to most of us, is back. Not as a way to stretch the expensive blooms in a bouquet but on its own, as a big breathy explosion of little white fleurs. And on this snowy day, that’s not a bad explosion to think about.