Write results computed by several algorithms for the same request
simultaneously for a given medium. This allows to have only one CSV line
for a given request.
To achieve that, the class ResultList was created.
CalibrationRequest::operator==() was not marked as const, which caused
trouble with unordered_set.
This commit corrects also CalibrationRequest::operator!=(),
Result::operator==() and Result::operator!=().
Matteo Cypriani