Bug 21629: Use cn_sort instead of itemcallnumber when displaying a list

Bug 21629: Use cn_sort instead of itemcallnumber when displaying a list

DBMS can sort callnumbers correctly using cn_sort. We should use it
showing a list's content.

Test plan:
- Add items with callnumber to a list
- Display the list
- List the content by callnumbers
=> Confirm that the records are correctly sorted by callnumber

Signed-off-by: Myka Kennedy Stephens <mkstephens@lancasterseminary.edu>

Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>

Signed-off-by: Nick Clemens <nick@bywatersolutions.com>