finished gpu module docs for matrix reductions
finished gpu module docs for matrix reductions


apavlenko/opencv,opencv/opencv,opencv/opencv,opencv/opencv,apavlenko/opencv,apavlenko/opencv,apavlenko/opencv,apavlenko/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,opencv/opencv,apavlenko/opencv