Enforce fullCalcOnLoad. closes #427

[JanMarvin]

If a formula in a workbook originally created by Excel refers to a cell modified by openxlsx2, the formula was not recalculated when loaded in Excel. The formula was update only if the cell was visited and Enter was hit. This was hard to spot could easily result in errors. This was solved enforcing fullCalcOnLoad.

This also brings revisionPtr simply to reduce visual differences when comparing two files.

[JanMarvin]

This should be correct, though it is not universally available.

• Excel simply does nothing without it, works fine with it
• LibreOffice 7.4 seems to handle it partially. It works on a single sheet, but not with secondary sheets
• Numbers simply ignores the calculation properties, therefore no issue is visible