Added notification about printing a report with the ability to extend the content of the printed document.

The V9Preview1 API adds functionality to insert XML markup into a report before printing to allow plugins to extend the content of the printed document.

A notification has been added to INotificationService DocumentInvoicePrinting notification with the following parameters:

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

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