Bug 31824: Add page-section to list of pending/received orders (acq)

Bug 31824: Add page-section to list of pending/received orders (acq)

This patch adds a "page-section" class to the divs wrapping two
sections on the "Receive orders" page in Acquisitions.

To test, apply the patch and go to Acquisitions.

- Locate a vendor and view its details.
- In the toolbar, click "Receive shipments."
- If you have existing shipments listed in the first section, click the
  invoice number link.
  - If not, fill out the "receive a new shipment" form and submit it.
- On the "Receive orders" page there should be two sections: "Pending
  orders" and "Already received."

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>