removed outdated data_generator and data_distributor

src/data_handling/__init__.py

src/data_handling/advanced_data_handling.py

src/data_handling/data_distributor.py

src/data_handling/data_generator.py

src/data_handling/data_preparation_join.py

src/data_handling/data_preparation_neighbors.py

src/data_handling/station_preparation.py

test/test_data_handling/test_bootstraps.py

test/test_data_handling/test_data_distributor.py

test/test_data_handling/test_data_generator.py

test/test_modules/test_training.py