FeatureFinderMultiplex

The FeatureFinderMultiplex TOPP tool can detect peptide features in MS1 data. It is particularly suited for the analysis of labelled experiments, such as SILAC or Dimethyl labelling. The main algorithm was previously submitted in pull requests #868 and #889. - This pull requests contains the user interface, calculation of the fold changes and the export to the final data formats: consensusXML, featureXML and mzQuantML. 
If you are worried about checking the input too often for release builds, you can also use `OPENMS_PRECONDITION` which has a nice contract-type design to it. Basically you would have everybody calling the function promise to fulfill the precondition and you can safely work with the knowledge that all your explicit assumptions are fulfilled. This would be more developer-oriented while throwing exceptions is more user-oriented and with the idea that you can potentially recover from this case

Just as a comment how one could also do it - the way you do it here is also fine I think