User:Liangent/wb-lang/updates

Merged

 * Language work infrastructure is done (class LanguageWithConversion, LanguageFallbackChain and LanguageFallbackChainFactory). 70871 71778
 * Repo: A new special page, Special:MyLanguageFallbackChain, is added, to display the language fallback chain used for current context, allowing users to confirm their user settings now. 71281

Pending

 * Client: is now able to display labels from variant languages, as properly converted text. 71072 71996
 * Repo: Serialized formats get a new field "source-language", alongside with "language", to indicate the language where this particular piece of data was fetched. A new pseudo language code, "qqc", is introduced to contain the most preferred label for current context. 71787 71182
 * Repo: Various page titles, including view, edit and history, as well as displayed text of links to item pages (on special pages), are better displayed. 71845 71865