Bug 29397: Add .kohaSelect select2 wrapper function

Bug 29397: Add .kohaSelect select2 wrapper function

This patch adds a kohaSelect wrapper function to simplify
paging/infinite scrolling with select2 using the Koha RESTful api's.

Invoke select2 select boxes as you normally would from JS, but instead
of calling .select2(config) use .kohaSelect(config).

If an 'ajax' property is defined in your config object, we wrap the
transport such that responses include a pagination key as expected by
select2.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>