Scott D. Pierce: Chuck Lorre’s latest sitcom, ‘B Positive,’ is positively good

Never, ever underestimate Chuck Lorre. The last time the uber-producer created or co-created a network TV comedy that didn’t run for at least four seasons was 28 years ago. And he’s had nine on the air since then.His latest show, “B Positive” (Thursday, 7:30 p.m., CBS/Ch. 2), which he co-created with Marco Pennette, gets off to a very strong start. It’s yet another twist on the comedy trope of a mismatched couple, but it’s so well done it feels fresh — a