Refactor and don't initialise much of Core when in Protostellar mode

We don't need most of Core for Protostellar.  All code related to configuration management, for instance, should be moved.

Similarly, we don't need, AFAICT, CoreEnvironment's scheduler - it's an unnecessary thread pool.

Perhaps we should look at making Core into an abstract base class and having CoreClassic and CoreProtostellar implementations.  Similar for CoreEnvironment.