UI Nits: Reinstate drop shadow option

But NOT for win32 and ONLY on the sidebar and tabwidget (for
performance reasons). Since most users prefer the tabbed look
anyway this should be ok.

Performance of the graphicseffect has improved remarkably in
the 2 years since we tried it before. Worth experimenting with
since it adds a bit of polish to the look and feel.

Users turn it on and off in options, it is off by default.

src/HomeWindow.cpp

@@ -217,6 +217,15 @@ HomeWindow::HomeWindow(MainWindow *mainWindow, QString name, QString /* windowti
     // watch drop operations
     //setMouseTracking(true);
     installEventFilter(this);
+
+#ifndef WIN32
+    // add a drop shadow to the window
+    if (appsettings->value(this, GC_DROPSHADOWS, false).toBool() == true) {
+        QGraphicsDropShadowEffect *dropShadow = new QGraphicsDropShadowEffect(this);
+        dropShadow->setBlurRadius(10);
+        tabbed->setGraphicsEffect(dropShadow);
+    }
+#endif
 }
 
 HomeWindow::~HomeWindow()