Data import - better error messages
"This data file is not usable with vTAS!"
Please give more details ! E.g.:
- if the file is in a valid format but the instrument is not in the list, this must be clearly stated.
- other messages: "This file contains no data" if the step number is 0, "xxxx parameter not found", etc.
- at least, always give the line number at which at problem was found.
When the input has failed, there should be a reminder somewhere in the interface. Why ? Because an oblivious user may think that the old plot is the new plot (I already experienced that). The best would be to erase the contents of the panel 'Scattering plane', but this is not compatible with the current interface design. So we have to think about it.