This is still a rather horrible proof, though. More work to be done.

this makes it slightlymore annoying to use because we have to elliminate the box. one more reason to have a proof mode ;-)

* Put level of the triple at 20, so we can write things like
  ▷ {{ P }} e @ E {{ Φ }} without parentheses.
* Use high levels for P, e and Φ.
* Allow @ E to be omitted in case E = ⊤.

This fix removes superflous white space in pretty printing. For example
✓{S n} x was pretty printed incorrectly as ✓{(S n)} x.

Still need to use it everywhere.