Sets the start date for this item.  This will automatically push the
        end date to match the duration for this item.  So if the item starts
        on 1/1/12 and ends on 1/2/12, and the start date is changed to 2/1/12,
        the end date will change to 2/2/12.  To affect the duration of the 
        item, use either setDuration, or setDateEnd.
        
        :param      dateStart | <QDate>

def setDateStart( self, dateStart ):
        """
        Sets the start date for this item.  This will automatically push the
        end date to match the duration for this item.  So if the item starts
        on 1/1/12 and ends on 1/2/12, and the start date is changed to 2/1/12,
        the end date will change to 2/2/12.  To affect the duration of the 
        item, use either setDuration, or setDateEnd.
        
        :param      dateStart | <QDate>
        """
        dateStart = QDate(dateStart)
        
        duration = self.duration()
        self._dateStart = dateStart
        self._dateEnd   = dateStart.addDays(duration - 1)
        self.markForRebuild()