Realtime honours color settings

Updated the realtime plots and dials to use the colour
settings from the ride plot. So if you prefer plots of
light colours on dark backgrounds you can do this now.

The use of colour on the telemetry values makes it easier
to distinguish which value related to power et al .. especially
when you're pushing out that last max power interval.

src/VideoWindow.cpp

@@ -23,6 +23,7 @@ GcWindow(parent), home(home), main(parent)
 {
     setControls(NULL);
     setInstanceName("Video Window");
+    setProperty("color", Qt::black);
 
     QHBoxLayout *layout = new QHBoxLayout();
     setLayout(layout);