[IMP] web_kanban : Improvement in Kanban header.make dropdown and kanban...

... record length seperate
- Task: https://www.odoo.com/web#id=10055&view_type=form&model=project.task&menu_id=3942&action=327
- Pad: https://pad.odoo.com/p/r.SXTI5j4Swq6MN3Mn