code: public MappingImpl cloneReadOnly(ConfigImpl config) {
  	return new MappingImpl(config, virtual, strPhysical, strArchive, inspect, physicalFirst, hidden, true, topLevel, appMapping, ignoreVirtual, appListener, listenerMode,
  		listenerType);
      }
docs: clones a mapping and make it readOnly
  
  @param config
  @return cloned mapping
  @throws IOException