add debit note on receivable_sales_payment

new file on
web/application/
- controllers/credit_note.php
- helpers/credit_note_used.php

web/application/views/receivable_sales_payment/add
- html.php
- js.php

alter file on
web/application/controllers/
- receivable_sales_payment

web/application/helpers/
- recalculate.php
- sales_payment_engine.php