Added new color toning method "L*a*b* regions"

Allows to specify various "regions" of the image with masks, and to correct
for hue, saturation and lightness.

Inspired by the existing L*a*b* grid (in turn taken from darktable)

rtengine/rtthumbnail.cc

@@ -1363,6 +1363,7 @@ IImage8* Thumbnail::processImage (const procparams::ProcParams& params, eSensorT
     ipf.chromiLuminanceCurve (nullptr, 1, labView, labView, curve1, curve2, satcurve, lhskcurve, clcurve, lumacurve, utili, autili, butili, ccutili, cclutili, clcutili, dummy, dummy);
 
     ipf.vibrance (labView);
+    ipf.labColorCorrectionRegions(labView);
 
     if ((params.colorappearance.enabled && !params.colorappearance.tonecie) || !params.colorappearance.enabled) {
         ipf.EPDToneMap (labView, 5, 6);