The `filterNodes` function's name and type signature were confusing, so
they were changed to make it evident that the filtering function for an
antry is applied to its total number of cooccurrences.

`occurrencesWith` takes a function parameter to map over the input
collection before counting occurrences. Every time it's called, though,
it's with `identity`, so I replaced the function with a basic occurence
counting function.

Note that if one needs to apply a function to a collection before counting
occurrences, they can simply `fmap` over the collection first.

Basically, Gargantext.Prelude exports all of Protolude now.

Based on the suggestions in
https://kodimensional.dev/space-leak

[CLEAN] adding signatures, removing unused imports, fixing shadowing...

                                                      distributional)
        Prelude: ideas on $ and & removed, kept in git history anyway.