Update fix of normalize_D in the case of wo weights. Add density plot in compute results for all stages and add some plots in results.

- Add new results for stage4.

- Add stage4 (results and experiments);
- Do not save model object.

- Remove extracted_forest_sizes_number parameter from compute_results.py and retreive the value instead;
- Add almost all remaining experiment config files of stages 1, 2 and 3;
- Add almost all remaining result plots of stages 1, 2 and 3;
- Add some temporary scripts to run all stages experiments.