This PR contains API changes alongside convenience and performance features:
* BlueCast & BlueCastRegression do not require the target column name during class instantiation anymore.
* t-SNE & PCA plots will scale input data automatically if not disabled by the user
* add `eta` param in grid search fine tuning
* raise `max_depth` in Xgboost param default
* add category encoding orchestration: If cardinality of a categorical column is below/equal a certain threshold, onehot encoding will be assigned, otherwise target encoding