[IMP] kanban :- improve css of fold and unfold columns.
[IMP] kanban :- improve css of fold and unfold columns.

havt/openerp-web,havt/openerp-web,akretion/openerp-web,akretion/openerp-web,havt/openerp-web,akretion/openerp-web,havt/openerp-web,havt/openerp-web