====== FDR Estimation ======

There are several ways to calculate FDR depending on the database search type. In Proline the FDR is calculated at peptide and protein levels using the following rules:
  * if the Search has been done on a concatenated Target/Decoy bank, FDR =  2 * nbr DecoyPSM / (nbr TargetPSM + bnr DecoyPSM ). Note: when computing PSM FDR, peptide sequences matching a Target Protein and a Decoy Protein is taken into account in both cases.
  * if the Search has been done on a separated Target/Decoy bank, FDR = nbr DecoyPSM  / nbr TargetPSM.