add columns to table "URI", "expected unit", "expression of unit" etc.

[magelm]

          > The columns can also be further split (as actually, that is a great idea), but I would require some time to do that.

Thank you and understandable! As it is a different topic, I suggest to open a seperate issue for this.
When the topic of elevation/ description is done, we can close #28, while the new issue is still valid.
This way the addition of new columns can also be referenced in the new version/ next release that the table will include more columns, e.g. URI of source description, expected value/ unit and expression of unit/ value etc. and users can add comments or suggestions for more/ other columns as well to the same issue.

currently, we have 5 rows:

we would need at least one more row:

and we should think about if recommended or expected "unit" should be a seperate column as well (in red; BUT this would be a different issue)

Originally posted by @magelm in #28 (comment)