Credit and charge notification emails

Two small things that should cut down on the "was I credited?" and "what's this charge?" emails.

When you apply a credit or adjust a balance, there's now a checkbox to email the customer the amount and the reason from your note, missing item, quality issue, whatever it was. Same on a one-time charge: they get a receipt with your note on it. Instead of a mystery line in their payment history, they get a plain email saying what it was and why.

The email is prefilled from the amount and note, and you can edit it right there before it sends or just leave it. There's a store-wide default behind the default link if you want the box pre-checked (or not) every time.

One more fix tucked in here: the note you type on a one-time charge is now what the customer sees on their account and receipt. It used to get replaced with the payment gateway's "I00001 Successful" response, so customers couldn't tell what a charge was for. Now your note shows up as written.