Aesthetic Tweaks

.. tile mode highlights on mouse over for a more
   fluid feel, and better feedback

.. can customise the trend view charts background

.. fixed a SEGV on apply preset in chart setup

.. this is part of a set of updates to update the
   standard setup to be more complete so the user
   can pretty much run off a standard config.

src/TreeMapPlot.cpp

@@ -100,7 +100,7 @@ TreeMapPlot::paintEvent(QPaintEvent *)
 
     // Init paint settings
     QPainter painter(this);
-    QColor color = GColor(CPLOTBACKGROUND);
+    QColor color = GColor(CTRENDPLOTBACKGROUND);
     QPen pen(color);
     pen.setWidth(10); // root
     QBrush brush(color);