UI: Allow volume peak to be customized via .qss

With the addition of the peak volume indicator, themes may wish to change
these colors but there was no way to do so. This change updates the
VolumeControl widget to allow a stylesheet to adjust all possible colors
for the volume bar. In addtion, the Rachni theme is updated to demonstrate
this new capability.

UI/volume-control.cpp

@@ -255,6 +255,26 @@ void VolumeMeter::setPeakHoldColor(QColor c)
 	peakHoldColor = c;
 }
 
+QColor VolumeMeter::getClipColor1() const
+{
+	return clipColor1;
+}
+
+void VolumeMeter::setClipColor1(QColor c)
+{
+	clipColor1 = c;
+}
+
+QColor VolumeMeter::getClipColor2() const
+{
+	return clipColor2;
+}
+
+void VolumeMeter::setClipColor2(QColor c)
+{
+	clipColor2 = c;
+}
+
 
 VolumeMeter::VolumeMeter(QWidget *parent)
 			: QWidget(parent)