[CLEAN] mail: remove unused import
[FIX] mail: chatter: display blockquotes with normal font size (appearing for example when replying through thunderbird).
[FIX] mail: invite: name of the document was missing in the link to access the document, leading to 'Access False'.
[IMP] mail: various cleaning and fixes in the notification email links (wording, missing document name management)
[FIX] website_forum: convert answer to comment, use superuser

To browse the forum post, as the partner of the create_uid of the post is needed, which can't be read by portal users.