Normally I would make sure this is not by default, or at leat disableable; but
here the code we print may contain utf8 anyway, so the terminal really needs to
support it. Anyway, it's just a little fancier, doesn't add much.
a quick fix for now, ideally we want an option for editor-friendly output.
But for now this is a very cheap way to at least have clickable error messages
which are a big time-saver.
This is a workaround (but corresponds to what was executed before) and means
that we re-explore all exprs to look for free variables.
The proper fix will be to store boxed_exprs inside scopes instead.
These are just variable renumberings, and type error message changes but still
pointing to the same information; the latter are slightly better in general,
pointing to actual expressions rather than scope declarations.
Before: `ELEMENT in SET`; now: `SET contains ELEMENT`
Using the `in` keyword was causing conflicts and blocking #203.
Current proposal has `contient` for the French syntax, and is untranslated (`contains`) for Polish.
I removed the '.out' extension for now to preserve the test output file names and avoid a million file renames.
This makes the patch easier to read, and we can do the rename easily in another patch afterwards, without mixing with semantic changes.
(beautiful script àlarrache:
```bash
for f in */*/output/*; do
target_base=${f##*/}
target_base=${target_base%%.*}
echo $f | awk -F. '{
f=$1"."$2; if ($4 == "") { mode=$3; id=$3 } else { scope="-s "$3; mode=$4; id=$3"."$4}
printf "\n```catala-test {id=\"%s\"}\ncatala %s %s\n```\n",id,mode,scope;
}' >> $(dirname $f)/../${target_base}.*; done
```
