Update contact details checks what customers type, and protects their account

Customers can correct the email, phone and name on their order. An empty or malformed entry is refused with a plain message instead of being saved, and a blank email box never deletes the email already on the order. With "Also update the customer's account" turned on, the account's email and phone change only when the customer is signed in to their own account; a change made from an order link updates the order alone. When an account email does change, the previous address is told.