removal of the class ACMeasurementPhaseDifference  according to our latest conceptualization of voltage. n.b we still have the conceptualization of 'acmeasurementphasedifference' which is ic-tplg:ACMeasurementPhase. - removal of the individual of acmeasurementphasedifference according to our latest conceptualization
-removal of long series of blank nodes with restrictions (erroneously produced by protege in the script file)