RoPs (Rotational Projection Statistics) feature

https://github.com/strawlab/python-pcl/blob/master/examples/official/Features/rops_feature.py

논문 : Yulan Guo, Ferdous Sohel, Mohammed Bennamoun, Min Lu and Jianwei Wanalso “Rotational Projection Statistics for 3D Local Surface Description and Object Recognition”