Basic doxygen documentation support

- updated existing Doxyfile.in
- added corresponding cmake instructions
- added some specific files (layout, icon)
- clean existing doxygen warnings

Conflicts:
	CMakeLists.txt
	doc/CMakeLists.txt
	modules/core/include/opencv2/core.hpp
	modules/core/include/opencv2/core/base.hpp
	modules/core/include/opencv2/core/cuda.inl.hpp
	modules/core/include/opencv2/core/mat.hpp
	modules/core/include/opencv2/core/matx.hpp
	modules/core/include/opencv2/core/types.hpp
	modules/flann/include/opencv2/flann/lsh_table.h
	modules/imgproc/include/opencv2/imgproc.hpp

modules/features2d/include/opencv2/features2d/features2d.hpp

@@ -415,7 +415,7 @@ public:
          * @param orientationNormalized enable orientation normalization
          * @param scaleNormalized enable scale normalization
          * @param patternScale scaling of the description pattern
-         * @param nbOctave number of octaves covered by the detected keypoints
+         * @param nOctaves number of octaves covered by the detected keypoints
          * @param selectedPairs (optional) user defined selected pairs
     */
     explicit FREAK( bool orientationNormalized = true,
@@ -814,6 +814,8 @@ class CV_EXPORTS FastAdjuster: public AdjusterAdapter
 public:
     /**\param init_thresh the initial threshold to start with, default = 20
      * \param nonmax whether to use non max or not for fast feature detection
+     * \param min_thresh
+     * \param max_thresh
      */
     FastAdjuster(int init_thresh=20, bool nonmax=true, int min_thresh=1, int max_thresh=200);