Bug 7288: add filter on subscriptions in the invoices table

Bug 7288: add filter on subscriptions in the invoices table

This patch adds a checkbox "Show only subscriptions" in the invoices
table.

If this checkbox is checked, only invoices that contain at least one
order linked to a subscription are displayed.

To test:
- Test in a database with multiple existing invoices
- Create an order from a subscription, close basket, receive
- Test that the result table of the invoice search shows
  the new checkbox and that it works correctly

Signed-off-by: Paola Rossi <paola.rossi@cineca.it>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>