Bug 19191: Add ability to email receipts for account payments and write-offs

Bug 19191: Add ability to email receipts for account payments and write-offs

Some libraries are paperless and require all payment receipts to be emailed. Koha should give libraries the option to send email receipts if a patron has an email address. If a notice for the type of "credit" exists ( payment or writeoff ), then an email receipt will be sent.

These notices only support Template Toolkit syntax.

Test Plan:
1) Apply this patch and dependencies
2) Add the two new notices, you can find them in installer/data/mysql/en/mandatory/sample_notices.sql
3) Note two new notices exist in the notices editor, ACCOUNT_PAYMENT and ACCOUNT_WRITEOFF
4) Find or create a patron with an email address that owes some amount of money
5) Make a payment for one or more fees
6) Note a new email is queued for the patron
7) Make a writeoff for one or more fees
8) Note a new new email is queued for the patron

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>