Payment notification processing has been updated

[E-junkie_Chef]

1. E-mail notification has been improved to provide formatted order and buyer information.
   
2. E-mail notification now includes the discount codes used.
   
3. Fee amount is now logged for PayPal Pro payments as well.
   
4. E-checks will be processed even if product price has changed during the the time of purchase and time when e-check clears.
   
5. Reversal and Refund handling has been improved to deal with PayPal's buggy multiple (not duplicate) IPN behavior.