Bug 10856: Improve the previous and next items on the shelf browser

Bug 10856: Improve the previous and next items on the shelf browser

The next and previous links should completely refresh the shelf.

For example:
[<] [1] [2] [3] [4] [5] [6] [>]
Before this patch, the next and previous links were the same as the 1
and 6.
With this patch, after clicking on next, we will get:
[<] [7] [8] [9] [10] [11] [12] [13] [>]

This patch adds a new AJAX script to get the shelf browser block.

Test plan:
- On a detail biblio page, click on a "Browse shelf" link.
- Play with the next and previous links.
- Deactivate Javascript (using NoScript for example) and check that you
  get the same behavior (but the page is reloaded).
- Launch the unit tests: prove t/db_dependent/ShelfBrowser.t

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Passes all tests and QA script.

Signed-off-by: Galen Charlton <gmc@esilibrary.com>