refactoring

src/common.py

src/pages/1-samples_selection.py

src/pages/2-model_creation.py

src/pages/3-prediction.py

src/shared_cached.py

src/style/layout.py

src/utils/data_handling.py

src/utils/data_parsing.py

src/utils/dim_reduction.py

src/utils/regress.py

src/utils/varimportance.py