Keep the best model for each replicate

[valosekj]

Just a very hacky first implementation, saving the best model for each replicate:

modular_optuna_ml/testing/output$ tree
.
├── model_rep0_trial0.pkl
├── model_rep1_trial0.pkl
├── model_rep2_trial4.pkl
├── model_rep3_trial5.pkl
├── model_rep4_trial5.pkl
├── model_rep5_trial4.pkl
├── model_rep6_trial4.pkl
├── model_rep7_trial4.pkl
├── model_rep8_trial4.pkl
├── model_rep9_trial4.pkl
└── output.db