Engaging Networks Forms: Hidden Opt In field should have editable value

In EN forms v2, it is possible to put an opt in as hidden field, but it has the following problems:

• it doesn't get rendered in the page (as hidden field)
• In its edit part it doesnt' have a default value (which if it is hidden will be the one that will be submited).

Task:

• In the edit part of a hidden opt in field, add a value field
• include it as hidden field in the form

Part of the UAT is to test that the field is indeed gets submited to EN.