IDEAS

* Apply folding on all tasks, instead of one by one.
  - Feed first instances, nevertheless their task?

* Let -separator in extract to be a string and look it in the pcf?

* Detect that the end of the instance does not have counters!
  Warn at least during extract

* Automatically search in the slopes the performance counters responsible
  for the change in the MIPS rate.

* FIX
  boost::exception_detail::clone_impl<libparaver::UIParaverTrace::error>
  message is printed if the tracefile does not exist when using the -feed-first-occurrence

* class Options, that holds all options of interpolate.C

* class FoldingIO, that reads & writes .extract file

* class GNUPLOT generator?
   - remove gnuplot generation from isntance-group.C?