Extract files per assay

[sneumann]

For a multi-assay file, the extractor collects too many files. It would be great
if in the tool you can select an assay (just like in the ISA to W4M converter)
and, for maximum flexibility, the column with file names (e.g. Raw Spectral Data File or Derived Spectral Data File) and output that as a collection. Difficulty will be the File type.
Yours, Steffen