'Create if nessessary or get the existing datafield object with name \'name\' and return it.
If created, attributes \'type\' and \'label\' are applied to new datafield.'

def setField(self, name, typ=None, label=None):

    f = self.getField(name)
    if f:
        return f
    return self.addChild(node=DataField(name, None, typ, 0, label))
