OutputFileMedium is designed to be a super-class for classes that need
to write to a text file. It could also be a simple writer if the method
write_string_to_file() was public (maybe we should change that and
rename OutputFileMedium to OutputFileWriter or something like that).
InputLogCSV:
- Now extends InputLogMedium *and* OutputFileMedium.
- Make log_request() inline.
Matteo Cypriani