Custom objective names for a given set of goals

[Arastais]

Sets of goals (i.e. overall objectives) should be added into the script as curated objectives, sort of like presets or built-in challenges. Only the names has to be added for this feature, but ideally the player should be able to selected a curated objective or select "custom" and create their own as they do now.

The hard part would probably be figuring out how to integrate it into OpenTTD's config window, as GSInfo (in the GS API) is basically all that is available for this.