Improved security option for private key recover in Underscore Backup

Yesterday night I came up with a new way of handling subscriptions in Underscore Backup that now gives the option of not storing the email of an account anywhere in the service as long as you are ok with not receiving billing emails. This will improve the security for private key recovery since the service will now not have the information required to decrypt the key stored anywhere in the service as long as you disable billing emails about charges (You can still see your invoices on the website). By default this is disabled because I think most people will prefer the billing emails over the increased security this provides.