Stacy Hoilett is single. So is her younger sister, Aisha. Today, Valentine's Day, the two plan to ignore the barrage of commercials for flowers, chocolates and diamonds and party hearty with their single friends. ''Just because I'm single, it doesn't mean I'm sitting around the house waiting for the phone to ring,'' says Stacy, 30, a kindergarten teacher. 'We're not hanging around saying, `Poor us.' '' Aisha, 29, a third-grade teacher, agrees: ``It's just another day.'' In this era of reality television courtship shows like Average Joe and The Bachelorette, the acceptance of singledom may seem a bit odd. But...