Make dates respect current locale (deprecations!)

And make comments use it in a smart way (it's not but it works)

Deprecate "extra.date_format" and "extra.comments.locale" and replace it
with "date_format" and "date_locale" in translation files

templates/partials/comments.html

@@ -13,7 +13,7 @@
 {% endif %}
 
 {% set id = page.extra.comments.id %}
-{% set date_locale = macros_translate::translate(key="date_locale", default="en-GB", language_strings=language_strings) %}
+{% set date_locale = macros_translate::translate(key="date_locale", default="en-IE", language_strings=language_strings) | replace(from="_", to="-") %}
 
 <section id="comments">
 	{% if config.extra.comments.show_qr %}