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

* 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.

or with batch rendering

* Fixed type narrowing issues

This built correctly before because tests were run with the highgui module enabled.
The sfm module links against the features2d module, which brings in the highgui module as an optional target if enabled.
Through this path, imread was working correctly despite the file including the wrong header and not declaring its linking dependency.

* Fixed typo

* Resolved the typo and trailing space error

Expose line descriptor python (#1994)

* Created wrappers for other line_descriptor functions/classes

* Changes to expose LSD and EDLines params in Python and make line descriptor available in Python

* Fix spelling of perpectiveRemovePixelPerCell in struct docstring

* Fix spelling of perpectiveRemovePixelPerCell in detection tutorial