Split TrainedSupervisedModel into 3 classes (Base, Regressor, Classifier)

[Aylr]

Background

There is a ton of logic for classification only properties that is making maintenance burdensome. Extract out two new classes TrainedRegressor and TrainedClassifier (or other better names) that inherit from the TrainedSupervisedModel class. This will drastically clean up code, tests and make maintenance easier.