Treat Spanish and Chinese decks as distinct "objects"

[aplaice]

This arguably makes sense, since they have translated deck descriptions (unlike the other language decks).

Fix #565.

I'm not too happy about this because:

1. We're repeating ourselves considerably (most of src/headers/default.yaml is repeated).
2. While repeating ourselves we're duplicating the definition of the "Ultimate Geography" deck config (43d37fac-9a65-11e8-9cc5-a0481cc15658), which IMO should still be exactly the same for all decks.
3. We now have "separate" decks for only Chinese and Spanish (because these are the only decks with separate deck descriptions). (This arguably makes sense, and I'm least unhappy about it.)

[ohare93]

@aplaice this change should help lighten the duplication :+1: https://github.com/ohare93/brain-brew/pull/47

With this change you do not need an extra header yaml for the different languages, but can instead read in the same yaml file multiple times, with overrides for the description (which was already possible), name, crowdanki_uuid.

It took me 10 mins to do, but I did not get time to test it. It's pretty simple though :smile: Let me know if it works or not, and I can take a look tomorrow at the latest.

[axelboc]

Congrats on fixing (1) and (2)!

Re. (3), I think having separate decks makes sense, and seems to be what people expect (cf. https://github.com/anki-geo/ultimate-geography/discussions/564#discussioncomment-3448043). Sure, it's annoying that not all translated decks are separate at the moment, but it's temporary. If we agree that this is the way to go for future translations, then I think it's good to go!