Typos, displays and elegance corrrections to French localization.

Created by: el00ruobuob

@erciccione This follows reddit comment from /u/Criminales78 here: https://www.reddit.com/r/Monero/comments/8efifn/getmoneroorg_is_now_available_in_polish_and_french/ who trigered the fact that many typos were left behind. All "base" pages have been checked out. I keep the user-guide checkout for a later update, along with #692 translation.

Please, do not Merge before #697. Or tell me if i need to rebase onto upstream/master. Rebased as it was ugly.