Notes:
Translations for all languages in preferences' drop-down should be written in native language not depending from current locale. As for example, you can take Youtube language settings at the bottom of the screen. And user can choose a language he can actually read.
As all localisation strings go to "en" as a fallback, we can just remove locale translations from all localization files except "en"".
Moved hard-coded text in "backend" and "system" to the language files
(English and Dutch). Affected pages: administrator management,
administrator group management, system updates, system settings, email
settings. Also made some strings more generic for general use (like
"Saving...." instead of "Saving administrator account...")
Sergey Karavay
Vojta Svoboda
Alwin Drenth
Jens Herlevsen
Alwin Drenth
Jérémy Gaulin
Samuel Georges
krisawzm
Stefan Talen
sajjad-ser
Jasper