Informative error messages

[Deleetdk]

If one requests data it cannot find, one gets a non-informative error:

Error in dst_find_val_id(meta_data = meta_data, variable = names(query)[i],  : 
  All the values_text could not be matched in the text field of the values column of IELAND. It might be a typo or maybe the value isn't present in the variable.

It would be better if this also told you which values could not be matched. Makes debugging much faster.