Clean notebooks & update table names

fairnb/api/dbrepo.py

fairnb/entity/dbrepo_entity.py

fairnb/entity/entity.py

fairnb/executor.py

notebooks/1_audio_files.ipynb

notebooks/2_generate_features.ipynb

notebooks/3_aggregate_features.ipynb

notebooks/4_split.ipynb

notebooks/5_ml_model.ipynb

notebooks/main.ipynb

resource/1_audio_files/record_metadata.yml