introducing image calibration
We could merge those two modules into one?
https://git.embl.de/grp-bio-it/image-analysis-training-resources/blob/markdown/modules/image_pixel_content.md https://git.embl.de/grp-bio-it/image-analysis-training-resources/blob/markdown/modules/calibration.md
Not sure it would be too much information? I would not like to remove the 3D aspect, because also all the downstream modules work on both 2D and 3D data. That is, I do not distinguish much between 2D and 3D images, because I think all the concepts work for 2D and 3D, thus there is no need to repeat everything later for 3D (rather always immediately also do in 3D seems better to me).