LDEV-3689: Once a spreadsheet is marked it cannot be changed by the learner. This is done by removing the save button on the learner interface and by checking the status in the save method (which is also triggered by the finish button).
LDEV-3689: Updates current spreadsheet row when saved, rather than creating a new row every time. This stops the marks (linked to the spreadsheet) being lost when the spreadsheet is saved after marking. Also fixed the monitor's view screen so that it has the learner's own spreadsheet not the generic lesson spreadsheet.