display full license URL for the currently displayed EULA (bnc#898647)

- include the license file name in the URL

- directory listing has been disabled after moving registration licenses
from `nu.novell.com` to `updates.suse.com`

- 3.1.51
NTH: maybe better

    return nil unless location_is_url?(license_file_print)
    unless UI.WidgetExists(:printing_hint)
      log.error "No widget id X"
      return nil
      ... continue ...
    end