Bug 29394: Remove flatpickr instantiations from most of the tt files

Bug 29394: Remove flatpickr instantiations from most of the tt files

We must reduce the instantiations as much as possible to take advantages
of the default values and specific behaviours we have defined in
calendar.inc

This patch is suggesting to have a .flatpickr class and using the data
attributes:
- flatpickr-futuredate
- flatpickr-pastdate
- flatpickr-enable-time
- flatpickr-on-close-focus

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