Considering laser range_min when raytracing free space.

This is extremely useful when using simulated 2D laser from Velodyne (otherwise obstacles close to robot are raytraced and robot may hit something). I'm not sure if it's useful in general but might be...

I also added correct transformation into transformLaserScanToPointCloud -> if transformed into sensor frame then it doesn't make sense (one can use simpler projector). This should be correct and may improve costmap accuracy for robots moving at higher speeds :)