Changeset 6974 for trunk/sources/HeuristicLab.Problems.DataAnalysis/3.4/Interfaces/TimeSeriesPrognosis

#1081: cleared up definition of accuracy metrics for time series prognosis to make the distinction between one n-step forecast and n one-step forecasts clearer. Implemented calculators for time series accuracy metrics to support the calculation of the average accuracy over m n-step forecasts and adapted the unit tests accordingly.