document config settings

[bertsky]

The many options in config_params are explained briefly in the comments under train.config_params. Perhaps these could be made more visible by placing the latter in the former, and referencing them in the README?

Also, 3 of these don't have a description yet:

https://github.com/qurator-spk/sbb_pixelwise_segmentation/blob/63fcb961898540f95cb347d43f8965ae65b8be3f/train.py#L59-L61

I.e.:

• activate both scaling and blurring
• rotate images by 90°
• activate both scaling and Otsu binarization