Fix internal blog

I tried to enable and use laboite's internal blog, and encountered several issues.

• laboite checks if laboiteBlogURL is 'undefined', this doesn't work if set to empty string in settings
• link to author's page is not well constructed (double '/' in url)
• when trying to consult an article, I get a blank page (Uncaught TypeError: user is undefined error in browser console)
• in PublicArticlePage: author name does not appear in title, and search icon tooltip translation is missing
• in publishersPage: user shows structure id instead of structure name

Currently, internal blog is still accessible in maintenance mode