Bug: Alpine cotation missing on ice climbing outing

[flob38]

Alpine cotation should be available when creating outing.
Ice cotation is the only one available.

[brunobesson]

OK, so the global_rating is not defined for ice climbing outings, indeed:

• https://github.com/c2corg/v6_api/blob/master/c2corg_api/models/common/fields_outing.py#L133 (maybe it should also be added in listing?)
• https://github.com/c2corg/c2c_ui/blob/master/src/js/constants/documentsProperties.json#L183 (which is a copy from what's in API)

So I guess the fix should be made on both sides. I tried modifying the UI only, and the gloabl_rating, when set, is not taken into account.

@cbeauchesne @lbesson @asaunier do you confirm? could you help with modifying the API? (I guess there is a little bit more than adding the fields, e.g. unit tests)

[brunobesson]

I mistakenly commited the branch on master, so little more pressure to fix this on the API side, otherwise, if we do not revert, users will be able to set the global rating on their outing, but it won't be taken into account :)