Update counts of fields and wells.

def update_counts(self):
        "Update counts of fields and wells."
        # Properties.attrib['TotalCountOfFields']
        fields = str(len(self.fields))
        self.properties.attrib['TotalCountOfFields'] = fields

        # Properties.CountOfWellsX/Y
        wx, wy = (str(x) for x in self.count_of_wells)

        self.properties.CountOfWellsX = wx
        self.properties.CountOfWellsY = wy

        # Properties.attrib['TotalCountOfWells']
        wells = str(len(self.wells))
        self.properties.attrib['TotalCountOfWells'] = wells

        # Properties.attrib['TotalAssignedJobs']
        self.properties.attrib['TotalAssignedJobs'] = str(self.count_of_assigned_jobs)