Bug 16238: Use .prop() instead of .attr() for 'checked'

Bug 16238: Use .prop() instead of .attr() for 'checked'

According to https://jquery.com/upgrade-guide/1.9/#attr-versus-prop-
.attr() is no longer correct to access the checked state of a checkbox.

This patch do the following replacements:
  .attr('checked')               =>  .prop('checked')
  .attr('checked, '')            =>  .prop('checked', false)
  .attr('checked, 'checked')     =>  .prop('checked', true)
  .attr('checked', boolValue)    =>  .prop('checked', boolValue)
  .removeAttr('checked')         =>  .prop('checked', false)
  .attr('checked') == 'checked'  =>  .is(':checked')

Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>