Merge branch 'lukas_issue298_feat_periodogram' into 'develop'

HPC_setup/requirements_HDFML_additionals.txt

HPC_setup/requirements_JUWELS_additionals.txt

docs/_source/_plots/periodogram.png

mlair/data_handler/data_handler_mixed_sampling.py

mlair/data_handler/default_data_handler.py

mlair/plotting/abstract_plot_class.py

mlair/plotting/data_insight_plotting.py

mlair/plotting/postprocessing_plotting.py

mlair/run_modules/post_processing.py

mlair/run_modules/pre_processing.py

requirements.txt

requirements_gpu.txt