WebHost: use a limited process pool to run Rooms

[Berserker66]

What is this fixing or adding?

Should drastically reduce the memory requirements on WebHost by consolidating Rooms onto a few Processes, instead of one each.

How was this tested?

A bit locally. Logging is entirely broken. Only on Windows 10 so far.

Future

I don't know how best to solve the logging problem. Ideas or PR'd solutions are certainly welcome. There's probably some data overlap between Rooms that can now be "exploited" to consilidate RAM use, I haven't checked, but I would guess that currently each room still has a full copy of its datapackage, with no sharing. There is one print in there currently, due to logging being broken and me otherwise not seeing the message.