Added notification for printing reports with the ability to extend the content of the printed document.

The API V9Preview1 has added functionality for inserting XML markup into the report before printing, allowing plugins to extend the content of the printed document.

In INotificationService, a notification DocumentInvoicePrinting has been added with the following parameters:

IDocument - Passes the type and number of the printed document.

ChequeExtensions - Used to insert XML markup into the corresponding sections of the document (BeforeHeader, AfterHeader, BeforeFooter, AfterFooter).