Add atmos.speedup which is effectively a atmos-only time compression
CVar. This adjusts heat capacities and transfer rates to effectively
globally speed up the time constants of atmos.
This allows faster response to heating/cooling changes and faster
cleanups (by buffing scrubbers, pumps, and everything else) that is
tunable through one global time compression CVar.
It also achieves this without any thermodynamic unsoundness.
