Add `trim()` utility method

This method:
- trims strings on both sides via the native function;
- replaces multiple consecutive spaces inside strings by a single one;
- handles non-breaking space characters.
Add utility method to recursively trim arrays
Remove `trim()` method from MPList scrapers

The classes will now call the method inherited from their parent.
[refactor] Use `trimArray()` on MPList scrapers
Merge branch 'refs/heads/recursive-trim-method'
Move method

`trimArray()` is now after `trim()`.