Add dedicated buttons for scope switching

Previously, changing to a different scope was done by clicking the scope
type button and cycling through all scopes. This commit decreases the
number of clicks needed to switch between two scopes by adding a radio
selector. The radio buttons can be shown or hidden by pressing the scope
type button. This commit also makes the raw histogram one of the scope
types.

rtgui/options.h

@@ -317,11 +317,12 @@ public:
     };
     int histogramPosition;  // 0=disabled, 1=left pane, 2=right pane
     bool histogramRed, histogramGreen, histogramBlue;
-    bool histogramLuma, histogramChroma, histogramRAW;
+    bool histogramLuma, histogramChroma;
     bool histogramBar;
     int histogramHeight;
     int histogramDrawMode;
     ScopeType histogramScopeType;
+    bool histogramShowScopeButtons;
     bool FileBrowserToolbarSingleRow;
     bool hideTPVScrollbar;
     int whiteBalanceSpotSize;