When I was a bratty, fashion-obsessed pre-adolescent I would have killed for a store that, you know, spoke to me.    So even though I'm all grown up, I'm still excited to hear about Play Couture , a boutique opening in Beverly Hills this week. Catering exclusively to the 7-16 set, the store will carry collections by Miss Grant, LA Made, Miss Sixty, Diesel, Junk Food, K...