Use explicit names in some scripts, re-organize fupd plainly derived laws, adjust wsat import/export.

Modify adequacy proof to not break the 'fancy update' abstraction. Modify fupd plainly interface and add new derived results.

The BI interface is then instantiated using these laws.  In particular, this
shows that the rules we claim to be admissible actually are.

Show that atomic_step is an AccElim so we can open invariants; get entirely rid of the Em ⊆ Eo side-condition

Based on an earlier MR by @jung.

Assertions should have type sbi_car PROP and not bi_car (sbi_bi PROP).