Bug 34116: Add page-sectioning to item search in label creator

Bug 34116: Add page-sectioning to item search in label creator

This patch adds a "page-section" class to search results page seen when
adding items to a label batch. The patch also makes some minor changes
to markup around the search header to make it more consistent with other
search pages.

To test, apply the patch and go to Cataloging -> Label creator.

- Click New -> Label batch
- Without entering anything in the textarea, click the "Add item(s)"
  button"
- In the pop-up window, perform a search which will return multiple
  results.
- Confirm that everything looks correct and all controls work as they
  should.

Signed-off-by: Sam Lau <samalau@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>