Add Support for "Allow Other" in Original Attribute Enumerations

Dictionary based Attribute Enumerations offer an "allow other" option. However, the original Attribute Enumerations (CoPersonRole/OrgIdentity o/ou/title) do not support allow other via Enrollment Flows/Petitions. Support requires changes to

• AppModel::updateValidationRules()
• CoEnrollmentAttributesController::beforeRender()
• View/CoEnrollmentAttributes/fields.inc
• View/CoPetitions/petition-attributes.inc

The views should leverage enumerations and enumerableField View Elements.