Merge branch 'master' into glitch-soc/merge-upstream

Conflicts:
- app/controllers/settings/preferences_controller.rb
- app/lib/user_settings_decorator.rb
- app/models/user.rb

Conflicts due to the addition of a new preference upstream,
“advanced layout”.

app/javascript/mastodon/initial_state.js

@@ -20,5 +20,6 @@ export const version = getMeta('version');
 export const mascot = getMeta('mascot');
 export const profile_directory = getMeta('profile_directory');
 export const isStaff = getMeta('is_staff');
+export const forceSingleColumn = !getMeta('advanced_layout');
 
 export default initialState;