kitti2bag fix for #153

Make Velodyne/Ouster input format a config option

add parameter for base_link (see @2scholz  comments)

In a lot of setups the base_link does not coincide with the lidar frame.
For that reason a base_link parameter was added and the base_link is now
used as tracking frame.
The transform from the base_link to the lidar frame is taken into
account when sending out the odom to base_link transform.