Dedicated `Refresh.WorkerServer` project to facilitate workers

[jvyden]

This is so we can run workers independently, outside of the Refresh.GameServer executable.

Workers should still run as part of Refresh.GameServer by default, but they should be able to be disabled through the config.

[jvyden]

Extending this to include support different 'categories' or 'types' of workers, for the purposes of #864. We could have a C# worker doing all the normal gameserver stuff and a 'CwLib' worker that is able to handle stuff that requires Toolkit.