Merge branch 'develop' into 'lukas_issue298_feat_periodogram'

docs/_source/_plots/datahistogram.png

mlair/configuration/defaults.py

mlair/data_handler/data_handler_mixed_sampling.py

mlair/data_handler/data_handler_single_station.py

mlair/data_handler/default_data_handler.py

mlair/helpers/datastore.py

mlair/helpers/statistics.py

mlair/plotting/data_insight_plotting.py

mlair/run_modules/post_processing.py

mlair/run_modules/pre_processing.py

test/test_configuration/test_defaults.py