- read image as 1-channel grayscale
- 3 trackers to control function parameters
- K allowed to go to negative values (usually to detect black text on white bg)

- no for-loops
- support all thresholding types
- support any input image depth
- add Doxygen comments

otherwise we get a failed assertion from OutputArray::create

cvx::checkHardwareSupport uses static field to store flags.
Using a global static to store the result is dangerous, as the underlying field checkHardwareSupport uses might not be initialized at that time.

* Sparse match interpolator interface and EdgeAwareInterpolator were
added to the ximgproc module
* New optical flow algorithm, based on PyrLK sparse OF and sparse match
interpolation, is added to the optflow module

Now the filter natively supports StereoBM and StereoSGBM with no
parameter tuning required. Also, now user won't need to set the ROI and
the right matcher parameters manually, it is all done in the respective
convenience factory method based on the left matcher instance. Tutorial
was added to clarify the provided example of use.