TrafficSigns: [classification] Add a ConfusionMatrix to classification_eval script

[Christiaan1990]

Goal:

Update the evaluation script of the classification with a confusion matrix, such that more insights of the results are gained.

Assigments:

• obtain code from GiT
• add a confusion matrix plot (with def)
• test, and commit to GiT
• documentation how to use the notebook in the TUM-Wiki: https://wiki.tum.de/display/phoenix/Machine+Learning

Notes:

• See file "classification_eval.ipynb"
• https://scikit-learn.org/stable/auto_examples/model_selection/plot_confusion_matrix.html