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

Conflicts:
- app/controllers/oauth/authorized_applications_controller.rb
  Two changes too close to each other
- app/controllers/settings/sessions_controller.rb
- app/lib/user_settings_decorator.rb
  Two changes too close to each other
- app/models/media_attachment.rb
  New changes too close to glitch-soc only changes.
- app/models/user.rb
  Two changes too close to each other.
- app/services/remove_status_service.rb
  Kept direct timeline code which had been removed upstream.
- app/views/settings/preferences/show.html.haml
  Two changes too close to each other.
- config/locales/en.yml
  Introduction of a new string too close to glitch-soc-only's “flavour”
- config/locales/ja.yml
  Introduction of a new string too close to glitch-soc-only's “flavour”
- config/locales/pl.yml
  Introduction of a new string too close to glitch-soc-only's “flavour”
- config/locales/simple_form.en.yml
  Introduction of a new string too close to glitch-soc-only's “skin”
- config/locales/simple_form.pl.yml
  Introduction of a new string too close to glitch-soc-only's “skin”
- config/settings.yml
  Reverted upstream's decision of enabling posting application by default.

app/javascript/mastodon/features/compose/components/upload_button.js

@@ -63,7 +63,7 @@ class UploadButton extends ImmutablePureComponent {
             key={resetFileKey}
             ref={this.setRef}
             type='file'
-            multiple={false}
+            multiple
             accept={acceptContentTypes.toArray().join(',')}
             onChange={this.handleChange}
             disabled={disabled}