Improve default base classifiers

[luizgh]

By default, if the pool of classifiers is not informed in the constructor of the DS methods, a Bagging Classifier (with 10 decision trees) is used to generate the pool. However, better methods can be used as default, in particular Self-generating Hyperplanes (SGH) : https://www.sciencedirect.com/science/article/pii/S0031320318302802