[IMP] hr_department: new kanban view for HR Departments.

hr add a simple kanban view that is updated by the various hr modules.
Each module adds statistics and links in the kanban vignette, either
in a to do or to approve column.

The department kanban view can be seen as a small dashboard to have
the main data about the department displayed. Links allow the HR
manager to be redirected towards the various things to do or to
approve in its department.