- Refactor so that we can create RepositoryState in one place
and then reference to it from JpaRepositoryTransition impls.
- New common top class BaseRepositoryEntity for entities
- Change RepositoryState and RepositoryTransition to be abstract
classes instead of interfaces.
- New custom StateMachineJackson2RepositoryPopulatorFactoryBean and
StateMachineJackson2ResourceReader handling json refs.
- Relates to #262