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.

All the `env` operations are prefixed `env_`, so this is more consistent.

make atomic_acc typeclasses-opaque

Use telescopes for atomic accessors, updates and triples; improve mask handling; add notation for all of them

With a pretty proof by Robbert

make pm_maybe_wand a BI connective; reduce BI connectives and option combinators in the proofmode with cbn

* move PROP-envs definitions to environments.v so that we can control them without pulling in coq_tactics
* use reduction-controlled `pm_default` for proofmode accessors

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