private StandardEvaluationContext createEvaluationContext(Context aContext) {
    StandardEvaluationContext context = new StandardEvaluationContext(aContext);
    context.addPropertyAccessor(new MapPropertyAccessor());
    context.addMethodResolver(methodResolver());
    return context;
  }
a {@link TaskEvaluator} implemenation which is based on 
Spring Expression Language for resolving expressions.

@author Arik Cohen
@since Mar 31, 2017
src/main/java/com/creactiviti/piper/core/task/SpelTaskEvaluator.java