- Use cv::AutoBuffer rather than new allocation
- Fix "assignment operator could not be generated" warning

mask = cv2.inRange(hsv, lower_green, upper_green)
to
mask = cv2.inRange(hsv, lower_blue, upper_blue)

It could improve performance when image size is large.
E.g. OCL_PyrUpFixture_PyrUp.PyrUp/18

This flag is already added in line 131.

In the unoptimized version of small symmetrical column filters, when we
try to detect if the kernel, ky, is equal to [1;2;1] or [1;-2;1] we
should take into consideration that the anchor points in the middle
element.

- disabled doxygen tree
- enabled doxygen enum listing
- added imgproc reference to main page
- enabled BiB support
- chenged doxygen root page format

The function parameters were different from the ones described below.

P.S. Why is ``flow`` InputOutputArray, shouldn't it be just OutputArray? If so, shouldn't the reason be specified - e.g. so others can benefit as well (e.g. not allocating memory on every frame?)