Self Filtering for Kurt360

Small changes to enable proper self filtering with the rotation unit

- Modified the filter chain for the rotation unit in order to apply self filtering (requires self filter from TU
  Darmstadt (https://github.com/tu-darmstadt-ros-pkg/robot_self_filter.git))
- Removed footprint filter from laser_filters, since this became obsolete with introduction fo the self filter
- Added optional argument for rotunit launch file to use the top of hobbes robot instead of kurt360 top
change base_link to $(arg cloud_frame)