Prevent crash when updating files with entirely new internal data structure

[ghorwin]

When updating files (TSV and/or DataIO), a sanity check shall be made that verifies that essential data has not changed.

For TSV files the header must remain unchanged (not even unit changes). Otherwise a tsv file:

states.tsv#4|5|7 could have selected temperatures, yet now column 5 contains a relative humidity --> crash in the chart during update or bad data.

[ghorwin]

Testen, ob das nach dem Extractor-Umbau noch ein Problem ist!