Gail Collins: Ten candidates, no weather maps

OK, concerned citizens, it’s debate time. Come back here and sit down! This is important. Let’s see if you’re prepared.First, name the 10 Democratic presidential candidates who will be sharing the stage Thursday night. Give yourself a big pat on the back if you got them all. Light tap on the shoulder if you got six or seven.If you failed to remember Joe Biden, Elizabeth Warren and Bernie Sanders, just leave the room. Admit it. You’re not going to watch this thing at all,