Allow Skybox parameters to work with space_dynamic.yaml

Allow for Skybox parameters in space_dynamic.yaml to add their values to the generated playfield.yaml files.

For example:

Code:

Skybox:
    - [SunFlareWhite3Space, SkyboxStarsCyan, PrefabNebulaBlueYellow]
    - [SunFlareWhite, SkyboxStarsCyan, PrefabNebulaBlueYellow]
    - [SunFlareWhiteSpace, SkyboxStarsCyan, PrefabNebulaBlueYellow]
    - [SunFlareWhite3, SkyboxStarsCyan, PrefabNebulaBlueYellow]
    - [SunFlareRedSpace, SkyboxStarsCyan, PrefabNebulaBlueYellow]
    - [SunFlareBlue, SkyboxStarsCyan, PrefabNebulaBlueYellow]

Should pick one of those and add as an example this to the playfield.yaml file when it's generated like the pre-alpha 12 behavior:

Code:

SunFlare: EnvironmentalEffects/SunFlareRedSpace
Stars: SkyboxStarsRed
Nebula: PrefabNebulaBluePinkRed

This currently works if you manually add the skybox info to the playfield.yaml file in a scenario or save game, but there's currently no way to add this to space_dynamic playfields.
It can help add unique playfields, for example for when you want to simulate being in a different galaxy or alternate universe, to add mystery, or just because you want to use the old skyboxes instead of the new dynamic galaxy skybox.