[ticket/13041] Help_faq.php language file needs to be revised

Todo:
- [x] Reodering "login and registration issues"
- [x] Updating "login and registration issues"
- [x] Updating "User Preferences and settings" 
- [x] Updating "Posting Issues"
- [x] Updating "Formatting and Topic Types"
- [x] Updating "User Levels and Groups"
- [x] Updating "Private Messaging"
- [x] Updating "Friends and Foes"
- [x] Updating "Searching the Forums"
- [ ] Updating "Topic Subscriptions and Bookmarks"
- [x] Updating "Attachments"
- [x] Updating "phpBB3 Issues"
- [ ] Adjust/correct some answers to be compliant with new phpBB features

This is a WIP PR.
To be discuss.

PHPBB3-13041
Limited is correct: https://github.com/Skouat/phpbb3/commit/55e1f02151adbe9d66a2d87c00c4f1959739aa36#diff-11