Add preference setting for delete toot modal (#3368)

* Set delete_modal preference to true by default
* Does not show confirmation modal if delete_modal is false
* Add ja translation for preference setting page

app/views/home/initial_state.json.rabl

@@ -9,6 +9,7 @@ node(:meta) do
     me: current_account.id,
     admin: @admin.try(:id),
     boost_modal: current_account.user.setting_boost_modal,
+    delete_modal: current_account.user.setting_delete_modal,
     auto_play_gif: current_account.user.setting_auto_play_gif,
   }
 end