Remove multiple pcl::PointCloud <-> sensor_msgs::PointCloud2 conversions

on filtering (~20% faster)
Also adds a voxel grid side parameter to do more or less radical downsamples.

I have also changed verbose ROS_INFO to ROS_DEBUG when filtering.

Sorry for the other noisy changes: is just eclipse reformating the code on saving (tabs to spaces and remove trailing spaces). You can happily ignore.