- allow installing samples sources on all platforms
  even if BUILD_EXAMPLES is disabled,  fixed minor
  issues in sources installation process
- use 'example_<group>_<name>' scheme for target and binary file naming
- use single function for sample executable creation

- use per-module includes instead of "opencv.hpp"
- unused function warnings
- undefined macro warning

Found via `codespell -q 3 --skip="./3rdparty" -I ../opencv-whitelist.txt`

Remove unnecessary Non-ASCII characters from source code (#9075)

* Remove unnecessary Non-ASCII characters from source code

Remove unnecessary Non-ASCII characters and replace them with ASCII
characters

* Remove dashes in the @param statement

Remove dashes and place single space in the @param statement to keep
coding style

* misc: more fixes for non-ASCII symbols

* misc: fix non-ASCII symbol in CMake file

Fix bug in camera_calibration.cpp that the program tries to
parse input of type VIDEO_FILE as IMAGE_LIST which causes the
program to crash.

Original commit is a5f19f7dd6ae5bc93f73e0417a9e0bfd34c01672

in documentation exact path is images/CameraCalibration/VID5

see also PR #5393

in documentation exact path is images/CameraCalibration/VID5

    * correct the part about fixed aspect
    * improve formatting
    * add snippet markers to source
    * replace inline code by @snippet
  - do not run calibration twice when using a imageList
  - make output consistent in itself (CamelCase vs no_camel_case) as well as with old camera calibrate sample
  - respect write extrinsic/ points flags
  - set the aspectRatio value when specified
  - fix writing of calibration settings. also update grammar.
  - fix intendation and remove some size_t -> int casts by using size_t

quickly corrected the previous refactoring of features2d: moved from set(SOME_PROP, val) to setSomeProp(val)

1. someMatrix.data -> someMatrix.prt()
2. someMatrix.data + someMatrix.step * lineIndex -> someMatrix.ptr( lineIndex )
3. (SomeType*) someMatrix.data -> someMatrix.ptr<SomeType>()
4. someMatrix.data -> !someMatrix.empty() ( or !someMatrix.data -> someMatrix.empty() ) in logical expressions