Allow modify the public trial state also in closed dossier states


To achieve this, we implement a special edit form, which only handles the public trial field.
The link is only visible on the overview tab, if the dossier is in a closed state and the user has "modify portal content" permission in a open dossier state. 

- [x] Implement special edit form (for document and mail)
- [x] Implement edit button on overview tab (document / mail)
- [x] Translations
Well I did not know this usecase :smile:  I guess `Task` does not provide the IBaseDocument interface :smile: