[Feature Extraction] Orphan classes

[truonghoquang]

• extOrpCls (existence of orphan class in the diagram)
• noOrpCls (number of orphan classes in the diagram)
• avgOrpCls (no. of orphan classes / total no. of classes)

[truonghoquang]

This was solved just recently (check this commit) XMI structure: class => associationendtype