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/rtthumbnail.cc

@@ -1200,6 +1200,7 @@ IImage8* Thumbnail::processImage (const procparams::ProcParams& params, eSensorT
 
     ipf.firstAnalysis (baseImg, params, hist16);
 
+    ipf.dehaze(baseImg);
     if (params.fattal.enabled) {
         ipf.ToneMapFattal02(baseImg);
     }