Always send email prefs on register

For new members in Membership we need to pass the email preferences for a user on to Salesforce, these values can be accessed in the Identity API. Currently new registrations on Frontend are only passing email preferences that are checked (true). Unchecked values for registration are not passed and Identity do not set any value for email preferences. 

Rather than handle a null value in Membership I thought it would be more appropriate for Frontend to send the desired value (true or false) for email preferences on registration.