Types that need to be deserialized during configuration need to ensure valid id values

[jecollins]

As part of updating the sample broker for use in experiments, it becomes necessary to specify TariffSpecifications and other domain types in configuration files. A simple way to do this is to use the xml-serialized form in a configuration file. In this context, id values are not valid; they need to be set by calling the IdGenerator during or after the configuration process. Also, types that use id values as references (like Rate, which stores the id of its TariffSpecification) will need to update those id values during configuration.