Check that all {exercises,solutions} work in universes mode.

[sishtiaq]

[markulf]

How do we turn on universe mode in the tutorial. Should we do this globally, or selectively for a subset of the tutorial examples?

[beurdouche]

I think we could simply doing progressively from the beginning.
Maybe we can simply have a big red line saying: "WIP : From that point the tutorial hasn't been updated to the Universes syntax and is likely to change..." ?