Allow "make open access" on request copy reponses a disableable field

[drn05r]

In a response to a copy request for a restricted document there is a "make open access" checkbox. This is only presented if the user can edit the record in the live archive, so does not allow them to do something they could not otherwise do. However, the user may not fully consider the implications before checking this box. Whereas, making this change manually (editing it in the eprint workflow) they would be fully aware of what they are changing. Therefore, it should be possible to prevent this checkbox being displayed to avoid this potential issue.