VZooming Changes

1: Guard zone 8 pixels wide in VRuler to reduce risk of accidental use.
2: VerticalZooming preference, for VRuler zooming, off by default,
3: Enabled Paul's right-click menu in VRuler with some extra
presets (x2 and x0.5)
4: Rearranged some messy code with lots of ifs to use a switch.

Also, with EXPERIMENTAL_HALF_WAVE defined we now get a
'half wave' option in the VRuler menu, that shows the wave top half.
We also use it in collapsed waves (and collapsing and restoring
a WaveTrack will get you back to normal zoom.

src/WaveTrack.h

@@ -162,6 +162,8 @@ class AUDACITY_DLL_API WaveTrack final : public PlayableTrack {
    void SetVirtualState(bool state, bool half=false);
 #endif
 
+   void SetMinimized(bool isMinimized) override;
+
    int GetWaveColorIndex() const { return mWaveColorIndex; };
    void SetWaveColorIndex(int colorIndex);