KZ filter

Implement kolmogorov zurbenko filter for preprocessing. Should be callable like the tranform method inside the data generator as method of the data preparation class. First implementation can be found here: https://gitlab.version.fz-juelich.de/leufen1/kolmogorovzurbenkofilter . But this implementation has to be adapted to the current situation.

NOTE: regard that a gaussian filter is not proper (because values are used for baseline, that are not available at the forecast point of time). -> use left side of gauss curve and a hard cut-off.