Integrate Paolo's code of method 'Ensemble selection from libraries of models' by Rich Caruana et al

Speedup similarity forest regressor and add parallelization at the extracted forest size level in the training

Fix parallelization and estimator default hyperparams in kmeans and similarity methods. Fix on resume mode in train.py. Fix stage5 saving (tmp) in compute_results.py

Add on resume mode for the experiment training (and set the overwrite of the resulting model of the experiment optional)

Add Paolo's first implementation of this paper: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2822360/

- Add new results for stage4.

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

Add quick working version of diamonds dataset to test that the improvement of OMP are consistent in other regression tasks.

- 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.