ControlContext :: defaultOrder - Get default order key name
The default order is the order defined by the data source of the control. The default order may be changed by calling changeDefaultOrder(). When the data source for the control is unordered or does not support an order key, the function returns an empty string.
Return value: Key name ( odaba::String & )
The key name is the name of a valid collection index (order) or key defined for the data type in the database model.