Added editable Multilanguage Support
New config entry language: must be the same as in /public/lang/
EN (fallback) and DE for now.
Multilang: Fixed last hardcoded messages. Everything should work now.
Clicking multiple times mark/star and also 'Mark as read'.
(New span with data-attributes in helpers/ViewHelper.php added to pass
values from f3 to jQuery)

Also added datestrings and french translation from Yann Bogdanovic
(ianbogda). Credit and thanks to him!