* translation system and unit tests
* Translations everywhere
Dont use translation merge
It is not available with PHP builtin gettext, so it would have lead to inconsistency.
Use php-intl extension to display datetimes a bit more nicely, depending on the locale.
What changes:
* the day is no longer displayed
* day number and month are ordered according to the locale
* the timezone is more readable (UTC+1 instead of CET)