Avoid adding a stretch to the layout each time the properties change

in the property window.
As this causes the property widget to move each time the user clicks on a
processor.

application/gui/properties/propertycollectionwidget.cpp

@@ -63,7 +63,6 @@ namespace campvis {
             propertyCollection->s_propertyAdded.connect(this, &PropertyCollectionWidget::onPropCollectionPropAdded);
             propertyCollection->s_propertyRemoved.connect(this, &PropertyCollectionWidget::onPropCollectionPropRemoved);
         }
-        _layout->addStretch(1);
     }
 
     void PropertyCollectionWidget::setupWidget() {