Add BOOST, 3D depth, and gradient-angle knobs

- BOOST: global display level multiplier (0.75 - 2.5, 1.0 default)
- 3D: pseudo-3D bevel/shading on bars, LEDs, peaks and curve (0 = flat)
- G-ANG: 3D gradient angle (-180 - 180, 0 = top-lit)
- Apply CURVING rounded corners to bars and peaks in BAR mode

Source/Analyser.h

@@ -33,6 +33,8 @@ public:
     void setNumBands (int n) noexcept;
     void setTilt (double amount) noexcept { tilt = amount; }
     double getTilt() const noexcept { return tilt; }
+    void setBoost (double amount) noexcept { boost = amount; }
+    double getBoost() const noexcept { return boost; }
     double getGraceSeconds() const noexcept { return grace; }
     double getFalloffRate()  const noexcept { return falloffRate; }
 
@@ -79,4 +81,8 @@ private:
     // the centre of the log-frequency range.
     static constexpr double maxTiltDb = 18.0;
     double tilt = 0.0;
+
+    // Display boost: a global multiplier on the level the analyser shows
+    // (0.75 = quieter, 1.5 = louder, 1.0 = unity).
+    double boost = 1.0;
 };