Registers a plugin to handle particular column types and column names
        based on user selection.
        
        :param      plugin     | <XOrbQueryPlugin>
                    columnType | <orb.ColumnType> || None
                    columnName | <str> || None

def register(self, plugin, columnType=None, columnName=None):
        """
        Registers a plugin to handle particular column types and column names
        based on user selection.
        
        :param      plugin     | <XOrbQueryPlugin>
                    columnType | <orb.ColumnType> || None
                    columnName | <str> || None
        """
        self._plugins[(columnType, columnName)] = plugin