clear_tokens UI is not working

Problem/Motivation

The clear_tokens sub forms are not appearing (anywhere, I think) so you can not tell a display to not render empty tokens.

The clear_tokens code still seems to be fine, so if you change the defaults to TRUE in the config then empty tokens don't get displayed, it's just that you can no longer turn on/off the clear_token behaviour.

Steps to reproduce

1. install and activate v4.0.0
2. navigate to the 'manage display' of a content type
3. click on 'use inline formatter display', note that empty token replacement sub-form does not appear