ExtendedTableWidget: Make scrolling less awkward with lazy population

Improve the lazy population fatchData() calls when using the vertical
scrollbar to make scrolling a lot smoother. Still not perfect but
definitely a lot better than before.

src/ExtendedTableWidget.h

@@ -13,8 +13,12 @@ public:
 private:
     void copy();
 
+private slots:
+    void vscrollbarChanged(int value);
+
 protected:
     virtual void keyPressEvent(QKeyEvent* event);
+    virtual void updateGeometries();
 };
 
 #endif