[IMP] sale_timesheet: overview access

On sales order form view, we display a "project overview"
stat button. It redirects to the overview of the only
billable project of the SO.
To avoid access error, and because this dahsboard is usefull
only for project manager, only those ones will have access to
this overview. So, stat button (Sales order) and label on
project kanban are aonly visible for manager.