downloadversionIRdata: modifications to download_heatflux_mapping_reference()

- The points of the vertical target in 'X' and 'Y' get now shifted and rotated to appear on top of the horizontal target in order to avaoid overlap when plotting.
- Added new boolean peremter 'get_thickness=False' triggers optional calculation of distance of profile points to adjacent profiles. This is used to derive a thickness of the profile at each point for integration of heat loads.