Add clustering metrics

[kzkadc]

Description: added metrics for evaluating clustering results implemented in scikit-learn:

• silhouette score
• Davies-Bouldin score
• Calinski-Harabasz score

Check list:

• [x] New tests are added (if a new feature is added)
• [x] New doc strings: description and/or example code are in RST format
• [x] Documentation is updated (if required)