make showing something implicit

In tutorial, a lot of example needs :showexpr to see results.
But in ghci, there is no need to type show. You just type it and it will show what it is.

Sometimes, I just want to try some ideas to see if it is what I think.
relations, atoms, relational expressions and function applications are something I want to see the results immediately.

It may help people trying things in tutd.

Start with the tutorial and the tutd entry point, reviewing where :showexpr is currently required for relations, atoms, relational expressions, and function applications. The change is done when those results are shown implicitly in the tutorial workflow without requiring :showexpr, with the intended behavior confirmed for each listed expression kind.

Scritto dal modello di indicizzazione a partire dal testo della issue.