Bug 18542 - Move and style "new field" link in item search form

Bug 18542 - Move and style "new field" link in item search form

This patch modifies the item search page JavaScript so that the "New
field" link has a "+" icon and is always placed at the end of the last
row in that section of the form.

To test, apply the patch and open the item search form in the staff
client. In the third section there should be a "+ New field" link at the
end of the first row of fields.

Clicking the "New field" link should clone that row and move the link to
the end of the cloned row.

Behaves as expected.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Amended patch: Fix indentation