bar charts are not honouring the setLabelPosition

Hi, this one is easy!
the PhpOffice\PhpPresentation\Writer\PowerPoint2007\PptCharts.php::writeTypeBar does not honour series:setLabelPosition.

in line 982 adding:

``` php
$this->writeElementWithValAttribute($objWriter, 'c:dLblPos', $series->getLabelPosition());
```

seems to fix the issue (i just looked at the code for writeTypePie to see this.
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