Discription of the metadata in Grist

[Ly0n]

For the grist spreadsheet a description of the various metadata could help user a lot to understand the source / calculation of various values we are showing. Such a description could be added manually via the Grist front-end, or ideally should be added to the Python script that creates the columns in the first place, so that this data is stored in a repository and can be easily recreated.