Add data type for CustomerDataType

[andyg5000]

If email is required on the Authorize.net account, you must pass the email when issuing a refundTransaction. The data that needs to be added to the request is <customer><email="[email protected]"/></customer>'. There are also additional properties for the customerDataType` as seen in https://api.authorize.net/xml/v1/schema/AnetApiSchema.xsd