Add target quality score to the train page

**Is your feature request related to a problem? Please describe.**
There is only one visible parameter for the train process now, the `time to train` value.

**Describe the solution you'd like**
Now that we have many good quality indicators like `Accuracy`, `AUC`, `AUPRC`, `F1-score` for the trained models, it would be great to have a target quality score for the training, instead of just the maximum training time.
After this addition the user could define what his/her target - let's say - F1-score is, so the training could stop before the `time to train` timer expiration if that quality score is achieved.

**Describe alternatives you've considered**
I can now manually stop the training if I notice that the trained model is sufficient.