reorganize the inputs/csv and activities folders

[Remi-Gau]

At the moment all the csv and the activities are all on the same level.

Organizing them in subfolders might improve readability for both the csv and their corresponding activities

• core
• meeg
• mri
• artemis
• eyetracker
• pet

This will require some adaptation on the python conversion scripts to be able to get their input from somewhere but also write the jsonld files in the correct subfolders and match that to the correct relative path in the schema.

This will also require adapting the download csv script to download the files in the right folder.