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

rtgui/paramsedited.h

@@ -269,11 +269,9 @@ public:
 class HSVEqualizerParamsEdited {
 	
 public:
-	bool enabled;
-	bool sat[8];
-	bool val[8];
-	bool hue[8];
-	int	hsvchannel;
+        bool hcurve;
+        bool scurve;
+        bool vcurve;
 };
 
 class RAWParamsEdited {
@@ -321,11 +319,9 @@ class ParamsEdited {
         ColorShiftParamsEdited        colorShift;     
         LumaDenoiseParamsEdited       lumaDenoise;    
         ColorDenoiseParamsEdited      colorDenoise; 
-	
         DefringeParamsEdited          defringe;    
         DirPyrDenoiseParamsEdited     dirpyrDenoise;    
         ImpulseDenoiseParamsEdited    impulseDenoise;    
-
         SHParamsEdited                sh;             
         CropParamsEdited              crop;           
         CoarseTransformParamsEdited   coarse;