Deleting all entries pertaining to a particular experiment_run

[hemanklamba]

This functionality might be good to make control the size of predictions table. Might also help in removing unwanted (buggy) runs altogether from the database.

[rayidghani]

listing out which tables to drop rows from. we could do it everywhere but here's a starting point

1. triage_metadata.models
2. triage_metadata.model_groups
3. train_results.predictions
4. test_results.predictions
5. train_results.evaluations
6. test_results.evaluations
7. train_results.feature_importances
8. train_results.aequitas
9. test_results.aequitas

other high priority ones? should we log when this happens in case we find orphan model information later on?