Allow timesheets to be locked

Timesheets should be able to be locked so that changes cannot be made to them once payroll is processing. By not having this feature, discrepancies arise, and it is difficult to see when those changes are made. We currently cannot tell if an employee or manager made a change to a timesheet after the cut off time, or if the timecard report we are using has errors which is why the time is missing. It would be best practice to enable locking timesheets once a pay week is complete.