FEATURE: Localization fallbacks (server-side)

The FallbackLocaleList object tells I18n::Backend::Fallbacks what order the
languages should be attempted in. Because of the translate_accelerator patch,
the SiteSetting.default_locale is *not* guaranteed to be fully loaded after the
server starts, so a call to ensure_loaded! is added after the locale is set for
the current user.

The declarations of config.i18n.fallbacks = true in the environment files were
actually garbage, because the I18n.default_locale was
SiteSetting.default_locale, so there was nothing to fall back to. *derp*

lib/freedom_patches/translate_accelerator.rb

@@ -59,6 +59,11 @@ module I18n
       end
     end
 
+    def ensure_loaded!(locale)
+      @loaded_locales ||= []
+      load_locale locale unless @loaded_locales.include?(locale)
+    end
+
     def translate(key, *args)
       load_locale(config.locale) unless @loaded_locales.include?(config.locale)
       return translate_no_cache(key, *args) if args.length > 0