Article deletion - time and user should be configurable

Article deletion - time should be configurable

Since the latest update articels can only be deleted within 10 minutes.

see - https://github.com/zammad/zammad/issues/2687

This should be configurable.

  1. on / off
  2. time adjustable

As mentioned in #2687 - Administrators should still be able to delete articles.
This is also missing.

Better solution than Administrator would be if that could be set in the roles.