Add setting to split manager and additional manager permissions.

We encountered an issue recently where a document that was sensitive was viewed by the 'additional reports to' of an employee, but we only wanted their top level manager to see it.

There is currently no setting to differentiate between the permission settings of the 'Reports to' and 'Additional reports to' managers of an employee.

There are situations where you would like a staff member to have an additional reports to for things like signing off holiday requests, but you don't want that additional manager to see all of the private documents of the employee.