Handle Paragliding rating

[AntoineMarnat]

https://forum.camptocamp.org/t/parapente-mise-au-point-de-lechelle-de-cotation/259456/50

It has been decided to use only 1 rating for paragliding.

[cbeauchesne]

Draft of a spec here : https://forum.camptocamp.org/t/parapente-mise-au-point-de-lechelle-de-cotation/259456/53?u=charlesb

[cbeauchesne]

Hide exposition => done

Split rating for takeoff and landing => Too much hack to be done only on UI side, we need to make an API modification (add new field, and rename the other one).

[cbeauchesne]

After further discussion, use the same property for both waypoint type, rename values, and limit to 4 levels : https://forum.camptocamp.org/t/parapente-mise-au-point-de-lechelle-de-cotation/259456/68?u=charlesb

[cbeauchesne]

Done. The limitation of the scale to [1-4] will be done on API side : v6_api#817