Fluid Internal Parallelism

- Added new graph compile time argument to specify multiple independent
ROIs (Tiles)
 - Added new "executable" with serial loop other user specified
ROIs(Tiles)
 - refactored graph traversal code into separate function to be called
once
 - added saturate cast to Fluid AddCsimple test kernel

modules/gapi/test/gapi_fluid_test_kernels.cpp

@@ -9,6 +9,7 @@
 #include <iomanip>
 #include "gapi_fluid_test_kernels.hpp"
 #include <opencv2/gapi/core.hpp>
+#include <opencv2/gapi/own/saturate.hpp>
 
 namespace cv
 {
@@ -72,7 +73,8 @@ GAPI_FLUID_KERNEL(FAddCSimple, TAddCSimple, false)
             for (int i = 0, w = in.length(); i < w; i++)
             {
                 //std::cout << std::setw(4) << int(in_row[i]);
-                out_row[i] = static_cast<uint8_t>(in_row[i] + cval);
+                //FIXME: it seems that over kernels might need it as well
+                out_row[i] = cv::gapi::own::saturate<uint8_t>(in_row[i] + cval);
             }
             //std::cout << std::endl;
         }