Lccp

This pull-request is part of the GSOC 2014 project of Markus Schoeler (Automated benchmark generation for object-part segmentation).

It contains an implementation of the lccp segmentation published in:
S. C. Stein, M. Schoeler, J. Papon, F. Woergoetter
Object Partitioning using Local Convexity
In Proceedings of the IEEE Conference on Computer Vision and Pattern Recognition (CVPR) 2014 

In addition, it contains an example "example_lccp_segmentation.cpp" which shows how to use the lccp segmentation.
That description is certainly outdated. Actually, both `PointXYZRGB` and `PointXYZRGBA` have exactly the same fields (which are created by line 177 [here](http://docs.pointclouds.org/1.7.0/point__types_8hpp_source.html#l00559)), so you can use `rgba` field for points of the former type.