Remember when hybrids were humble little cars, like the hunchback Prius? Well, hybridization has certainly jumped the shark when ponderous BMW 7 Series arrives in our garage with an electric motor buried in its power train. Yes, it is a technically marvelous machine, but does it really accomplish anything truly desirable? Or is this, as they say, a "halo product"? Brian Cooley takes you for a drive to check the tech.