enhanced elevation-only scans
enhanced elevation-only scans

- cardinal directions shown left/right on elevation scan x-axis
- altitude line drawn on map at 400 km to indicate show scan on map
- hidden altitude lines on flat plot
- drawn invisible coastlines on flat plot (otherwise the map axis isn't
  properly initiated)
- main plot title updated with new scan direction ('N-S' etc.)
- figure names updated with new scan direction ('N-S' etc.)

cmeeren/eiscatscanplot,cmeeren/eiscatscanplot