Refund full application fee if 'refund_application_fee' is set.

This is a temporary fix until stripe fixes their refund endpoint so that we don't have to do #768.
We use the existing flag on the refund endpoint to refund the full application fee whenever `refund_application_fee` is set.

Again, I had to make the same currency changes since my test account only supports CAD

@RichardBlair @odorcicd