text: Title: Add background command to download complete ingredient list
  Body: At the moment the command `python3 manage.py sync-ingredients` will download all ingridients from another wger instance, but this proces takes a looooooong time (several hours). We already have a version of this that runs on a celery queue every x months (`sync_all_ingredients_task`), but it would be really helpful if we could start this process manually with a mangement command `python3 manage.py sync-ingredients-async`