data/logic/ui: added aggregation edges

This change adds the creation of aggregation edges to the StorageGraph, which save the connection counts between
children in their parents. Aggregation edges are displayed using a straight line, that is thicker than more connections
it represents with the connection count in the middle.

src/app/qt/view/QtGraphView.cpp

@@ -246,7 +246,7 @@ std::shared_ptr<QtGraphEdge> QtGraphView::createEdge(QGraphicsView* view, const
 	}
 	else
 	{
-		LOG_WARNING("Couldn't find owner or target node.");
+		LOG_WARNING_STREAM(<< "Couldn't find owner or target node for edge: " << edge.data->getName());
 		return NULL;
 	}
 }