changed OpenCV license from BSD to Apache 2 license

* as discussed and announced earlier, changed OpenCV license from BSD to Apache 2. Many files still contain old-style copyrights though

* changed wording a bit; preserve the original OpenCV BSD license

[GSoC] New RANSAC. Homography part

* change enum and squash commits

* add small improvements

* change function to static, update magsac

* remove path from samples, remove license, small updates

* update pnp solver, small improvements

* fix warnings

* add tutorial, comments

* fix markdown warnings

* fix markdown warnings

* fix markdown warnings

Added and Edited specific information to the "Installation in MacOS" OpenCV documentation.
Closes #17340

* fixed #17044
1. fixed Python part of the tutorial about using OpenCV XML-YAML-JSON I/O functionality from C++ and Python.
2. added startWriteStruct() and endWriteStruct() methods to FileStorage
3. modifed FileStorage::write() methods to make them work well inside sequences, not only mappings.

* try to fix the doc builder

* added Python regression test for FileStorage I/O API ([TODO] iterating through long sequences can be very slow)

* fixed yaml testing

Updated the Windows Visual Studio Image Watch tutorial to include download links to the latest versions of Visual Studio Image Watch for newer Visual Studio versions.

Foumula fix 1

Foumula fix 2

Foumula fix 3

Foumula fix 4

Foumula fix 5

Foumula fix 8

* consolidate tutorials on image read/display/write

* fix unsused variables

* apply requested changes

* apply requested changes

* fix mistake

Update template_matching.markdown

Fixed "template image" should be "source image" in two sentences explaining template matching.

- Android Manager version is not increased (stuck on 3.49)

* add  python version of video-input-psnr-ssim

* remove ret

* documentation changes

* added link for python file

* command line argument

* fixed typo

* add compatibility code to handle migration

* delete old AndroidManifrst.xml

* fix tutorial generation

* Add python version of panorama_stitching_rotating_camera and perspective_correction

* Updated code

* added in the docs

* added python code in the docs

* docs change

* Add java tutorial as well

* Add toggle in documentation

* Added the link for Java code

* format code

* Refactored code

* Added java code for meanshift and optical_flow

* added java code for module video

* added appropriate spaces in codes

* converted absolute path to command line arguments

* added spaces at appropriate places

Python code examples for file IO in xml and yml format

* Initial "Pythonization" of file_input_output.cpp

* Moved file_input_output.py to correct location

* Nearly done Pythonizing file_input_output.cpp

* Python equivalent of file_input_output.py created

* Started Pythonizing camera_calibration.cpp

* Completed Python tutorial/sample code for file_input_output

* Resolved whitespace issues

* Removed tabs in file_input_output.cpp

* Patched import order and wrapped code in main function

* Changed string to docstring format in help file

* Updated link to Python example code

backport commit 659ffadd

* doc: added macOS installation guide

* doc: added clarification and corrections

* docs: introduction entry, lowercase file names and ids

G-API: Tutorial: Face beautification algorithm implementation

* Introduce a tutorial on face beautification algorithm

- small typo issue in render_ocv.cpp

* Addressing comments rgarnov smirnov-alexey

* G-API-NG/Docs: Added a tutorial page on interactive face detection sample

- Introduced a "--ser" option to run the pipeline serially for
  benchmarking purposes
- Reorganized sample code to better fit the documentation;
- Fixed a couple of issues (mainly typos) in the public headers

* G-API-NG/Docs: Reflected meta-less compilation in new G-API tutorial

* G-API-NG/Docs: Addressed review comments on Face Analytics Pipeline example

* G-API: Addressed various documentation issues

- Fixed various typos and missing references;
- Added brief documentaion on G_TYPED_KERNEL and G_COMPOUND_KERNEL macros;
- Briefly described GComputationT<>;
- Briefly described G-API data objects (in a group section).

* G-API: Some clean-ups in doxygen, also a chapter on Render API

* G-API: Expose more graph compilation arguments in the documentation

* G-API: Address documentation review comments