Investigate moving scan subsampling to an earlier step

[VorpalBlade]

It might be worth it to move scan sub-sampling earlier.

Currently it happens in MapLikelihood::update_importance, but at this point the point cloud has already been transformed via TF into a new coordinate frame.

Look into the possibility of doing this sub-sampling much earlier. It would require a rewrite of the laser_handler.cpp code, since currently this happens very early (in the call projector.transformLaserScanToPointCloud in LaserSub<sensor_msgs::LaserScan>::laser_callback, or externally for point clouds).