Currently, the JS views for editing an entity's terms are limited to ULS languages. We want to support more languages as content languages.
Current users of language data I found:
* wikibase.Site (used by jquery.wikibase.linkitem and jquery.wikibase.sitelinkview) needs dir
* getDirectionality (used by aliasview, descriptionview, labelview) needs dir
* getLanguageNameByCode (used by descriptionview, entitytermsforlanguagelistview, entitytermsforlanguageview, entityview, labelview) needs language codes and names