Refactor sample model; improve GUI

See merge request !528

Rename Transform3D -> RotMatrix

See merge request !530

Do not allow integration over Xi in Windows

Closes #160

See merge request !529

pointerize rotation

See merge request !527

rm node visitor

See merge request !518

Matthias Puchner authored 3 years ago and Wuttke, Joachim committed 3 years ago

"Error ~"... what kind of error handler shall this be? After changing to "replace", the encoding works much better