KinectFusion: several updates (#2133)

* truncateThreshold added

* demo updated for RealSense

* first Kinect2, then RealSense

* more distance-based parameters

Move background subtraction python tutorial to proper location (#2120)

* add tutorial from OpenCV-Python Tutorials

* remove trailing whitespace

* remove MOG2 part

* add cross-link to MOG2 tutorial

Incomplete sentence corrected. Resolves Issue #1997 (#2000)

* Incomplete sentence corrected. Issue #1997 

Resolves Issue #1997

``` FaceRecognizer::train(InputArrayOfArrays src, InputArray labels); ```

The type `InputArray` can accept `vector<T>` or `Mat` types as mentioned here: https://docs.opencv.org/3.4/d4/d32/classcv_1_1__InputArray.html

* Trailing whitespaces problem resolved

* Simplified quality API

* Compilation fixes

* test fixes

* Test updates

* Test fixes

* Fixed brisque data file location for install, test

* Increase error epsilon to account for multiple architectures

KinFu: try to fix OCL fails (#2106)

* some TODOs closed

* temporary turn on NaNs patching

* reverted

* temporary debug code added

* more debug code

* inf check; more debug code

* debug code in kernel

* debug code, try to disable some optimizations

* -cl-fast-relaxed-math option removed, debug code removed

reverts CUDA related stuff of commit ff0167b9

Update code after solvePnP and solvePnPRansac InputOutputArray changes

optflow: RLOF fixes (python-binding, status flag, flat textures) (#2097)

* * Bugfix for python-binding related to issue #2094. Copying the prevPtsMat to prevPoints was broken, when using python-binding.

* * Connect the blurred image correctly to CROSS support region segmentation. This allows to compute more robust support region shapes. Commit refers to issue #2094.

* * Bugfix to avoid the unintended assertion on flat textures discussed in issue #2094.

* * Bugfix on SparseRLOFOpticalFlow status was wrongly to to 0 if forward backward error < threshold, which is wrong. Inequation has been corrected. Refers to in issue #2087.

* small documentation changes

* bugfix on assertions and small test changes

* fix rectifyPatch bug when patch orientation is not extracted

avoid broken min/max macros from tesseract headers

If the disparity maps have the depth CV_32F, they are wls-filtered
in `DisparityWLSFilterImpl::filter` but the result is not saved in the
OutputArray of the method. Now, the result is copied to that array.