Calendar sidebar cosmetics

It should be white to be in line with the rest of the
sidebars and have some semblance of coherence.

I also put a rectangle around the box so if the day
color is white you can still see there is a ride that day.

A summary ala the interval summary will come next summarising
either day, week or month for the ride selected.

src/MainWindow.cpp

@@ -517,7 +517,8 @@ MainWindow::MainWindow(const QDir &home) :
 
     // RIGHT SIDEBAR
     gcCalendar = new GcCalendar(this);
-    gcCalendar->setStyleSheet("background: #B3B4BA;");
+    //gcCalendar->setStyleSheet("background: #B3B4BA;");
+    gcCalendar->setStyleSheet("background: white;");
 
     // TOOLBOX
     toolBox = new QToolBox(this);