Worker io refactor2

Implementation of the receiving (worker) side of the Json over standard IO refactor to use the IWorker interface.
@intern-felicco @abnanda1 @davidfowl 

The reference to the list is readonly however the collection itself is not. So you can modify the contents but you cannot replace the originally assigned list with a new instance. C# does not have a built-in concept of immutable collections (there is `ReadOnlyCollection<T>` class though)