Preprocessing includes building the InputSpace, checking the input dimensions and assigning the inputs to parameters.

Some surrogate strategies and PostProcessing options need to be reworked

Tested static training with PCE on analytical example, remaining changes tbd for sequential training and postprocessing

Initial split of the classes, MetaModel contains empty or general functions, PCE adds PCE/aPC specific options.
Training tested with User-guide example

Reduced the number of samples, walkers, etc for BMC for this example, so that the pipeline can run without exceeding the time limit