What is it?   We’ll say it now to curtail any suspense: you’re looking at the best driver’s car BMW produces. High praise, we’ll admit. But after a day spent lapping the new M2 CS around a circuit in Germany, we can’t think of any other current BMW that delivers quite the same combination of performance, balance and sheer attitude as this.   You’ll remember the M4 CS. This car takes the same philosophy. The M2 CS is a last hurrah for company’s junior M car prior to the introd