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Caustic Worlds - For Extremophile Species

Lithoids, Necroids, and now Toxoids feel like a bit of a missed opportunity to me. They represented a chance to implement species with wildly different biochemistries and environmental preferences to the game, but in practice they inhabit the same planetary environments as oxygen-breathing Mammalians, Reptilians, etc. And the Toxoids DLC's promise that we'd be able to inhabit Toxic Worlds ended up being rather underwhelming, simply referring to Toxic Worlds being terraformable into the existing planet classes once you've unlocked an ascension perk. This mod is an attempt to remedy this a little bit, without departing too far from the base game.

A new planet class is added: "Caustic Worlds", a form of Toxic World that is home to extremophile lifeforms which have evolved to withstand noxious gasses and crushing atmospheric pressure. These planets and moons are commonly found in the inner regions of a solar system, well inside the circumstellar habitable zone. While anyone can colonize them, most species will have 0% habitability by default and they tend not to have huge deposits of organic food.

There is also a new origin: "Extremophiles", for species that have evolved on a Caustic World and find them preferable to other planet types.
- Extremophile species have 80% habitability on Caustic Worlds and 60% on Tomb Worlds, but with a -20% penalty for everything else (except Gaia Worlds and the like).
- They can also terraform Toxic World Terraforming Candidates into Caustic Worlds once they have researched Climate Restoration, without having to take the Detox ascension perk.
- This origin cannot be combined with the Idyllic Bloom, Anglers, or Relentless Industrialists civics.
- This origin is only available to Anthropoids, Fungoids, Molluscoids, Lithoids, Necroids, and Toxoids.
- The Ix'Idar Star Collective now uses this origin instead of Prosperous Unification.

I am still working on balancing these mechanics, so please let me know what you think in the comments!