Allow sharing of arbitrary files

[vildead]

These can be:

• data dictionary
• manifest file (list of all files and folder structure)
• informed consent form template
• de-identification procedure followed when creating the dataset

This can be visible/accessible to logged-in users only. This ensures we have a log about user account accessing/downloading those in case of an issue. Example is EGA (metadata file) but there is probably more strict user verification step.