/scan topic inverted from expected rotational direction

[SteveMacenski]

The scan topic for a beam seems to rotate in the opposite direction as expected by the right hand rule / conventions in the sensor_msgs/LaserScan message. Obviously its unreasonable to ask that the lidar rotates in the other direction (well... can we do that?) so an easy solution is to have the lidar scan frame be inverted so the scan is 'virtually' set in the correct rotational direction. This is an easy and fast solution that other lidars that spin in the so-called incompatible direction can use laser scan tools in ROS correctly.

The issue is seen when working with 2D lidar SLAMs like gmapping and SLAM Toolbox which assume REP compliance of the LaserScan data. I was able to get around this by doing a pointcloud to laser scan conversion on a rotated, colocated frame to virtually invert the direction. However, that involves processing all the lidar data and I would prefer to use the driver's scan if possible.