Should be replaced with std::span when the compiler version
gcc >= 10, msvc >= 19.26 are available for development.

Mostly in the file headers.

find *Lib -type f | xargs sed -i 'N;s%^\s\+\*\n\(\s\+\*/\)%\1%'

Clang format run on near-the-header lines.

Happy New Year

This reverts commit 05677165.

Conflicts:
	FileIO/XmlIO/XmlGspInterface.cpp
	README.md

- added test programm for solving a linear system with CG-method
- time measurement is at the moment OS dependent!
- added Base folder
- added GeoLib folder
- added files in MathLib folder - restructured MathLib folder

- applying changes to interfaces