Updates is_wildfire column name to "label"

[fe51]

Thanks to #497 the is_wildfire column is more explicit allowing finer labelisation.

However, from now on, the name of the column is ambiguous. Indeed, the name is_wildfire makes one think of a boolean which is not anymore.

Would the name "label" more convenient ?
What do you think ?

Happy to discuss it !

[frgfm]

Agree, there are several topics to consider here but if this is no longer a boolean flag, the name should be changed
cf. #497 (review)