added haze removal tool

Based on the paper:
  "Single Image Haze Removal Using Dark Channel Prior" by He, Sun and Tang
using a guided filter for the "soft matting" of the transmission map

rtengine/procparams.h

@@ -1227,6 +1227,17 @@ struct SoftLightParams {
 };
 
 
+struct DehazeParams {
+    bool enabled;
+    int strength;
+
+    DehazeParams();
+
+    bool operator==(const DehazeParams &other) const;
+    bool operator!=(const DehazeParams &other) const;
+};
+
+
 /**
   * Parameters for RAW demosaicing, common to all sensor type
   */
@@ -1438,6 +1449,7 @@ public:
     HSVEqualizerParams      hsvequalizer;    ///< hsv wavelet parameters
     FilmSimulationParams    filmSimulation;  ///< film simulation parameters
     SoftLightParams         softlight;       ///< softlight parameters
+    DehazeParams            dehaze;          ///< dehaze parameters
     int                     rank;            ///< Custom image quality ranking
     int                     colorlabel;      ///< Custom color label
     bool                    inTrash;         ///< Marks deleted image