* removed private flann documentation
* common tutorial images moved to doc/images
* grouping issues

Found via `codespell -q 3 -S ./3rdparty,./modules -L amin,ang,atleast,dof,endwhile,hist,uint`

backporting of commit: 32aba5e6

Found via `codespell -q 3 -S ./3rdparty,./modules -L amin,ang,atleast,dof,endwhile,hist,uint`

Extend optical flow tutorial (#14314)

* extend python optical flow tutorial with cpp example code and add it to general tutorial directory

* remove unused parameters, fix comparison between signed and unsigned int

* fix hsv range problem

* switch to samples::findFile for sample file location

* switch to command line parameter for path

* remove old tutorial as in 14393

* minor fixes

Extend meanshift tutorial (#14393)

* copy original tutorial and python code

* add cpp code, fix python code

* add camshift cpp code, fix bug in meanshift code

* add description to ToC page

* fix shadowing previous local declaration

* fix grammar: with -> within

* docs: remove content of old py_meanshift tutorial, add link

* docs: replace meanshift tutorial subpage in Python tutorials

* switch to ref to fix wrong breadcrumb navigation

* switch to cmdline for path as in #14314

* Apply suggestions from code review

* order programming languages alphabetically

2) Added a raw Latex page break directive after each TOC tree. (For the PDF tutorial look).
3) Two finished tutorials: 
   a) one describing how the Mat data structure works and its output capabilities (format function) (demonstration YouTube video included).
   b) one describing image scanning operations plus the LUT function (demonstration YouTube video included). 
   c) a basic filtering approach (plus multi row image scanning demonstration) in the work.

New structure (following the documentation) for the tutorials. Normalized image sizes for TOC display.