Fix Processing Functions. Introduce custom target Parameter.

• Merge changes the register decorator to handles="index" and datamask="field", for all processing Functions, that do not alter the index.(Those are actually a lot)

• This is done to prevent those functions from demasking the processing results and thus, introducing flagged original values into processed timeseries

• Also, all processing functions got added custom target parameters, that just controll, where processing results shall be written to. (keeps flags, new data)

• Resampling functions, that implicitly use to_mask, got an explicit datamask='field' added to their decorators.

• pipeline currently fails due to toSequence being not able to handle None types - waitning for fix on multifields branch