public void setContextRepository(ContextRepository aContextRepository) {
    contextRepository = aContextRepository;
  }
A {@link TaskDispatcher} implementation which implements the parallel
construct. Providing a list of <code>tasks</code> the dispatcher will 
execute these in parallel. As each task is complete it will be caught
by the {@link ParallelTaskCompletionHandler}. 

@author Arik Cohen
@since May 12, 2017
src/main/java/com/creactiviti/piper/core/task/ParallelTaskDispatcher.java