suggested by Huge Herbelin

to avoid bad regressions, some other notations also ha to be tweaked

We already do the same for the goal, this avoids some scope
delimiters being displayed.

* 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

move test suite out of theories/ so it does not get installed; also check output of test suite so that we can test printing