Compatibility issue

Up to version 5.0, DataTables could contain Index elements that did not match the described IndexType. As from Version 4.5, this is not allowed anymore. 

The existing of wrong-typed Index elements in the context of a DataTable is probably due to copying (from Excel or another DataTable).

During automatic updating, the wrong-typed Index values are converted to the described IndexType. If this is not possible, the IndexType is set to string, conserving the orginal values in text-format.

Formulas depending on the Index column (such as VLookUp) did not evaluate properly in previous versions, and still won't due to the conversion to text. This means Futurama behavior is consistent with previous versions.