[Ovmsdev] MS_V_MOT_RPM

I’ve added a new standard metric (MS_V_MOT_RPM, v.m.rpm. StandardMetrics.ms_v_mot_rpm). This should be used to track engine/motor RPM. It is need by pretty much every OBDII tool out there, so makes sense for us to have it. In single-gear EVs, it can be output just after speed, via a simple scaling factor. Please try to implement it in your vehicle modules. Regards, Mark.