calculatedinvoice needs to contain VATtotal

[jstaerk]

which also needs to be parsed from CII and UBL,
when generated it's just

                BigDecimal VATtotal=BigDecimal.ZERO;
                i.calculate();
                for (VATAmount vam:i.getCalculation().getTaxDetails()) {
                    VATtotal=VATtotal.add(vam.getCalculated());
                }

... there might be a BT for that.