Fixes#350 and fixes#404
This change abandons validation via EditableFormField::validateField, as it bypassed too many core validation mechanisms (RequiredFields, etc).
In order to enforce consistency of editable field validation, display rules have been hard-disabled when a field is marked as required.
Since this removes functionality, I have incremented the major version number
Construct adds extensions, so calling functions which have extend calls in them before the parent:constructor means the extend calls will never find any extensions.
