[BUGFIX] Fallback to column name if no label is given for a column

If no label is given for a column as shown in the example below, the attribute "name" is not displayed in module Page nor in field "colPos".

    <flux:flexform.grid>
        <flux:flexform.grid.row>
            <flux:flexform.grid.column colPos="0" name="Main Content"/>
            <flux:flexform.grid.column colPos="2" name="Sidebar Content"/>
        </flux:flexform.grid.row>
    </flux:flexform.grid>