Add AdaBoost model and option to train on a subset of features

[luccalb]

Added the following:

• AdaBoost Classifier (DecisionTree under the hood)
• Option to select a subset of features for training in EVP demo
• Add results to documentation

[luccalb]

I didn't run it yet, but looks good. You could as well add in the documentation its performance.

Just added the docs :)