Show Voucher balance at customer account page

A small extension that adds a page to the customer account, where received gift vouchers and their remaining balance are shown.
Kind of like the transactions page, but for gift vouchers.

The gift voucher must have been sent to the same email address that is used as customer's username (which is probably true in most cases).

http://www.opencart.com/index.php?route ... n_id=11465