Creates a nesting tree of nodes, where the nodes represent the nesting of the loops. 

eOk if tree creation is successful.

• Return eOk if the loops count in OdDbMPolygon is zero.
• To avoid memory leaks use OdDbMPolygon::deleteMPolygonTree(loopNode).
• If loops in OdDbMPolygon were changed, get a new tree using this function.