Bug 10348: Show number of items on tab headings in the staff client

Bug 10348: Show number of items on tab headings in the staff client

This patch uses Template Toolkit's size() method to add a count to
the bibliographic detail page's holdings and images tabs.

To test, apply the patch and view the detail page for a record in
the staff client. Check under the following conditions:

- The SeparateHoldings system preference is set to "Don't separate"
  - The holdings tab should show the correct item count.
- The SeparateHoldings system preference is set to "Separate"
  - The "[Library] holdings" tab and "Other holdings" tabs should
    have the correct item counts.
- With LocalCoverImages enabled the "Images" tab should show the
  correct count of attached images. Test with zero or more attached
  images.

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>