Main module headers are moved 1 level up

e.g. <opencv2/core/core.hpp> become <opencv2/core.hpp>

Also renamed <opencv2/core/opengl_interop.hpp> to <opencv2/core/opengl.hpp>

modules/gpu/include/opencv2/gpu.hpp

@@ -50,9 +50,9 @@
 #endif
 
 #include "opencv2/core/gpumat.hpp"
-#include "opencv2/imgproc/imgproc.hpp"
-#include "opencv2/objdetect/objdetect.hpp"
-#include "opencv2/features2d/features2d.hpp"
+#include "opencv2/imgproc.hpp"
+#include "opencv2/objdetect.hpp"
+#include "opencv2/features2d.hpp"
 
 namespace cv { namespace gpu {
 

modules/gpu/include/opencv2/gpu/stream_accessor.hpp

@@ -43,7 +43,7 @@
 #ifndef __OPENCV_GPU_STREAM_ACCESSOR_HPP__
 #define __OPENCV_GPU_STREAM_ACCESSOR_HPP__
 
-#include "opencv2/gpu/gpu.hpp"
+#include "opencv2/gpu.hpp"
 #include "cuda_runtime_api.h"
 
 namespace cv