[FIX-#740] Fixed bug in IDPosteriorErrorProbability

Peptide with score 0 (e-value 10^99) will be ignored in the model testing and fitting, otherwise the program ends with the error. "unable to fit data. Algorithm did not run through for the following search engine: MASCOT".
The score 0 only will be ignored by a mascot search. To check if the changes are correct, I extended the Testfiles IDPosteriorErrorProbability_Mascot_input, IDPosteriorErrorProbability_Mascot_input2 with a PeptideIdentification that includes a PeptideHit which has the score=0 and e-value=1e+099 and created new output files for comparison. All tests for IDPosteriorErrorProbability were successful.