Build 3.5.0.104 of xlsgen preserves a number of calculation mode settings from existing XLSX files.

These are :
- calcMode (manual/auto)
- fullCalcOnLoad (bool)
- iterate (bool)
- iterateCount (number)
- iterateDelta (number)
- fullPrecision (bool)
- calcCompleted (bool)
- calcOnSave (bool)
- concurrentCalc (bool)
- concurrentManualCount (number)
- forceFullCalc (bool)

Preserving the settings makes sure that updating existing files with xlsgen does not change the expected performance of the spreadsheet (speed and memory) at run-time in Excel.