Hub and Spokes renamed to Entity and Components.

The Hub and Spoke classes have been refactored to something much simpler.
The previous Hub and Spoke were a little bit more general and difficult to understand due to templates.
The new Entity and Components don't use any templates are easier to understand.
However they are a little less general in that they depend directly on the libraries
which implement the components, and so will need to compiled into the components library.
The previous Hub and Spokes did not depend directly on the components and so could
stand on its own.