Bug 28942: Use Flatpickr on acquisitions pages

Bug 28942: Use Flatpickr on acquisitions pages

This patch modifies several acquisitions pages replacing jQuery
datepickers with Flatpickr widgets.

To test, apply the patch and test datepickers on the following
Acquisitions pages:

 - Acquisitions -> Late orders (linked date fields in the sidebar)
 - Acquisitions -> Invoices (linked date fields in the sidebar)
 - Acquisitions -> Invoices -> Invoice details (shipment date and
   billing date)
 - Acquisitions -> Vendor -> Receive shipment (shipment date)
 - Acquisitions -> Vendor -> Receive shipment -> Receive (on order line)
   -> Date received field under "Accounting details
 - Acquisitions -> Orders search tab in the header -> Advanced search:
   Linked date fields in the search form."

Signed-off-by: Lucas Gass <lucas@bywatersolutions.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>