* Remove allowed_languages and add filtered_languages

* Use filtered_languages instead of allowed_languages

* Update zh-CN translations.

* Update doorkeeper.zh-CN.yml

* Follow @Artoria2e5 's change advices.

* forget mail for text format ......

* fix some changes

* mail's html version ......

* https://github.com/tootsuite/mastodon/pull/2699#pullrequestreview-35982283

* a space.....

* delete some unused keys

* proofread & update zh-CN setting form locale

* Pull in new devise zh-CN translations from their wiki

https://github.com/plataformatec/devise/wiki/I18n,
more precisely https://gist.github.com/Artoria2e5/6d2a06ca9e92a417afc627b5000f4690

* pull in zh-CN translation for doorkeeper

... from https://github.com/doorkeeper-gem/doorkeeper-i18n/pull/31/