Flat curve editor widget, HSV tool modified to use it.

Usage :
 - click & drag a control point to move it in X&Y direction
 - click & drag a vertical line to move it in horizontal or vertical direction (the very first move will be used to determine the motion direction)
 - click & drag the yellow or blue square handle to modify the tangent of the same color

rtengine/procparams.h

@@ -370,16 +370,14 @@ class DirPyrEqualizerParams {
 };
 	
 /**
- * Wavelet equalizer params
+ * HSV equalizer params
  */
 class HSVEqualizerParams {
 	
 	public:
-		bool enabled;
-		Glib::ustring hsvchannel;
-		int sat[8];
-		int val[8];
-		int hue[8];
+		std::vector<double>   hcurve;
+		std::vector<double>   scurve;
+		std::vector<double>   vcurve;
 };
 
 /**