Add library for extracting primitives from pointclouds and a ros wrapper for it

This adds the ransac_primitives library for extracting primitives from a point cloud. It implements the paper "Efficient Ransac for Point Cloud Shape Detection" by R. Schnabel et al. At the moment, it only extracts planes but there is code for extracting spheres and cylinders that has just not been updated to the latest version of the framework. The primitive_extraction package serves as a wrapper around the library, supplying a launch file with lots of parameters and visualization in rviz via a marker array. The planes extracted will be used for finding tables.

The package is quite hard to try out since some of the parameters are tuned to the meta-room pointclouds. I will supply parameters good for normal Kinect images.