Move StarSystem slave cache from Galaxy to Space.
FillCache callback was not called when all objects already existed before.
Debug output.
Factions code no longer uses global Galaxy object.
CustomSystems code no longer uses global Galaxy object.
Galaxy generator and caches no longer use global Galaxy object.
Fix Galaxy object searching itself via Pi::GetGalaxy().
Space no longer uses global Galaxy object.
Merge two constructors of Game to avoid another Pi:GetGalaxy reference.