[1.04beta] Add a History Class - breathable atmosphere

[demiare]

So like in title - I'm suggesting a new History Class that forcing planet to have at least partially breathable atmosphere.

Why? It will allow us to simulate more planets from favorite Sci-Fi movies/stories/etc. Especially it's true for desert/icy worlds so popular in Sci-Fi, currently it's very hard to generate them with breathable atmosphere and without receiving a lot of forests/xeno-forests.

Surely, it isn't realistic but could be related for example with some GR terraformation experiments gonna rogue. Or instead successful attempt to cleanse hostile biosphere. I think it's possible to get some lore basis for having such planets around.