Refactor experiments

• rename baselines experiments
• merge all baseline model experiments into one file replicate_experiments.py
• move each model_dataset config to configurations.py
• create models.py with classes of each model to abstract instantiaion of each model.
• refactor evaluators.py so only single and competing events evaluator.
• clean up process_results.py
• add SurvTRACE and variants to replicate_experiments.py
• document