4.0.0-beta.6: fix avatar/logo i18n
- when the user's language is not the wiki's default language, display the default language's avatar and logo messages unless there are explicit avatar/logo messages for the user's language
- add extra space before endline comments
Change-Id: I0a91f0faff42f8c52b5a36d67b53e5e06fd5f3e6