Mid-way through the presentation of a new electric-vehicle at the Paris motor show on Thursday, Volkswagen made everyone watch an honest and rather heartfelt video whose theme was basically this: if you royally screw up you can either sit on your hands or try to change. VW’s doing the latter in a big way.Herbert Diess, head of the VW brand, pledged the world’s biggest maker of dirty diesels will completely change its spots: it plans to become the global market leader in electric cars instead.