Bug 28816: Improve the display of multiple holds during hold process

Bug 28816: Improve the display of multiple holds during hold process

This patch updates the appearance of the "confirm holds" page, shown
during the process of placing a hold for someone in the staff interface.

Most of the changes affect the appearance of the page when placing
multiple holds on titles which have one or more holds on them already.

The changes are intended to make the page clearer and easier to scan,
especially when placing multiple holds at once.

Also changed: The page heading when placing multiple holds now changes
based on whether you've selected a patron or not. It says "Search
patrons or clubs" when it's waiting for a patron/club selection. It says
"Place holds" after the patron/club has been selected. This is instead
of "Confirm holds" on both pages.

To test, apply the patch and rebuild the staff interface CSS
(https://wiki.koha-community.org/wiki/Working_with_SCSS_in_the_OPAC_and_staff_client).

- Go to Administration -> System preferences and set HoldsSplitQueue to
  "nothing."
- Perform a search in the staff client catalog and place multiple holds
  titles from that result set on hold for a patron.
- Perform the same search and select one or more of the titles you
  selected before in addition to one or more titles with no holds.
- After clicking the "Place hold" button you should see a page with the
  heading "Search patrons or clubs" showing information about existing
  holds. This section of the page should be clear and readable, with
  clear distinction between each section of information about each hold.
- Test this page again under each different option for the
  "HoldsSplitQueue" system preference by changing the preference and
  reloading the page.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>