Alias chest_gem -> chest_jewel

The bulk update request #11720 has been approved by @evazion.

create alias chest_gem -> chest_jewel

Same thing. Forehead jewel already has an alias like this, too.
Though, it might need to be reversed, as right now jewel is aliased to gem.

agreed on reversing it

The bulk update request #11720 (forum #219029) has been approved by @evazion.