This class provides a way to find out what entities are contained in
what transaction. It is used, to find which entities to call ejbStore()
on when a ejbFind() method is called within a transaction. EJB 2.0- 9.6.4
also, it is used to synchronize on a remove.
Used in EntitySynchronizationInterceptor, EntityContainer
Entities are stored in an ArrayList to ensure specific ordering.