Item1999: EditTablePlugin should handle CALC in header and footer same as it does in labels

This is a follow up bug to Item8230

We implemented a feature that shows SpreadSheetPlugin CALCs as the static text CALC during editing.

This is to avoid columns getting very wide when editing.

This was implemented for label columns and label fields.

Later it was added to header and footer but the code that protects labels is not the same that protects headers and footers so the result was that the static text CALC was saved after an edit.

I disabled the feature for headers and footers as a quick fix for Item8230.

This feature follows up on getting things right for header / footer but at a non urgent priority.

-- KennethLavrsen - 02 Sep 2009