Filter on allowed user language preferences (#2361)

* Naive approached to timeline filtering

* Convert allowed_languages into a db column

* Allow users to choose languages to see statuses in

* Style list items as two columns

* Add a hint to explain language filtering preference

app/controllers/settings/preferences_controller.rb

@@ -25,7 +25,8 @@ class Settings::PreferencesController < ApplicationController
 
   def user_params
     params.require(:user).permit(
-      :locale
+      :locale,
+      allowed_languages: []
     )
   end