Do no longer returns a PDF when a report is printed

Instead, a notification is displayed to the user.
When report.get_pdf() is called on a report that must be printer,
it will print the report *and* returns the pdf, thus code that
calls directly report.get_pdf() will print the pdf on the printer
as expected.

Fixes #16

base_report_to_printer/__openerp__.py

@@ -35,6 +35,7 @@
         'security/security.xml',
         'printing_data.xml',
         'printing_view.xml',
+        'base_report_to_printer.xml',
         'wizard/update_printers.xml',
     ],
     'installable': True,