[Ovmsdev] v.e.drivetime and v.e.parktime candidates for persistence

Hi Michael, I'd propose that v.e.drivetime and v.e.parktime should be persistent. Each time my OVMS reboots - whether deliberately or due to a crash - these timers are lost so its common that they are wrong. I know the space is limited but I think it would be much better if they survived a reboot. Steve