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/editorpanel.h

@@ -145,6 +145,7 @@ public:
     ) override;
     void setObservable(rtengine::HistogramObservable* observable) override;
     bool updateHistogram(void) const override;
+    bool updateHistogramRaw(void) const override;
     bool updateVectorscopeHC(void) const override;
     bool updateVectorscopeHS(void) const override;
     bool updateWaveform(void) const override;