Rename or delete "staging" and "production" stages

[aronneagu]

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• [x] I am running the latest version. (up upgrade)
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It would be nice to be able to rename the default stages, or alternatively to remove them. My company would like to use dev, stg and prod, as stage names, and having "staging" and "production" alongside "prod" and "stg" will only cause confusion.

[tj]

Fair enough! At the moment they're hard-coded in and can't be removed, I'll see if I can figure out a nice way to allow for that.