Bug 28983: Use Flatpickr on various pages

Bug 28983: Use Flatpickr on various pages

This patch replaces the use of jQueryUI's datepicker on various
unrelated pages.

To test, apply the patch and test the following pages to confirm
that datepickers work correctly. "Linked" date fields should prevent a
"to" selection which preceeds the selected "from" date.

- Tools -> Patron clubs -> New club: Linked "start date" and "end date"
  fields.
- ILL requests: Two linked pairs of date fields in the sidebar, "Date
  placed between" and "Updated between." Each pair should work correctly
  and table filtering by date should work correctly.
- Tools -> Label creator -> Manage -> Layout batches -> Edit a batch ->
  Add items. This should trigger a popup window with a linked pair of
  date fields, "Added on or after date," and "Added on or before date."
- Point of sale -> Transaction history: "From" and "To" linked date
  field in the "Older transactions" section.
- Acquisitions -> Suggestions -> Add a suggestion: "Created by,"
  "Accepted on," and "Managed by" fields.
- Tools -> Tags -> Filter tags by date.

Signed-off-by: David Nind <david@davidnind.com>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>