GitLab

- Notation for types
- Notation for pack and unit
- Better (?) levels for the relational judgement

Now with one rule primitive we can prove several instances that allows
us to eliminate
- Fancy updates
- Basic updates
- Laters

Add a pre_solve_closed ltac that basically changes the goal from
`Closed X e` to `Closed ∅ e`. It is actually OK in practice.