Bug 35329: move patron search to modal - Add guarantor

Bug 35329: move patron search to modal - Add guarantor

This is the first of many patches to come.

We will rewrite the patron search popup to convert it to a Bootstrap's modal.

I faced different problems on different pages, it is preferable to test
each page on top of the whole patchset, to make sure a futur change will
not break previous pages (and this is why they are all on the same bug
report).

For each page we will test that:
* the different filters work
* the "Clear" filters button work
* the "Add" or "Select" patron button works
* the nested modal to display patron's details (when clicking on their
  name or cardnumber) works

On this patch we are testing the guarantor search:
Create a edit a patron and click "Add guarantor" to open the modal.

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>