Issue an error if a CSV file that is to be imported is missing one or more required columns. Added a unit terst for this - DSoilModelIO_ImportFromCsvFileWithMissingHeaders(). Added and improved several messages in the Translations.xml file.
This new unit test caused a small typo/error in the CSV file for the DSoilModelIO_ImportFromCsvFileWithInvalidHeaders() to surface.
The soil type column must be made visible again - this will be done in the next commit. Related to Issue [DSB-500]