Documenting folder structure

[seltmann]

@mostwald I suggest that the readme explicitly list every folder in order that is in the repository. These should generally be listed in the same order they appear. If a series are folders for images, those could be grouped together.

Folder x is an image folders. Images can be found at (zenodo archive).

Also it is not totally clear that the Image Segmentation corresponds to a folder. I would name the headings exactly the same name as the folder name with a description that it includes folder contents. Image_Segmentation folder contents

[cantbelieveimshook]

I forgot to update the README accordingly. I'll do that.