Add repository config substates

- Add parent state to RepositoryState
  and use it in model factory.
- Relates to #262

spring-statemachine-data/src/main/java/org/springframework/statemachine/data/RepositoryState.java

@@ -23,6 +23,13 @@ package org.springframework.statemachine.data;
  */
 public interface RepositoryState {
 
+	/**
+	 * Gets the parent state.
+	 *
+	 * @return the parent state
+	 */
+	String getParentState();
+
 	/**
 	 * Gets the machine id.
 	 *

spring-statemachine-data/src/main/java/org/springframework/statemachine/data/RepositoryStateMachineModelFactory.java

@@ -62,7 +62,7 @@ public class RepositoryStateMachineModelFactory implements StateMachineModelFact
 
 		Collection<StateData<String, String>> stateData = new ArrayList<>();
 		for (RepositoryState s : stateRepository.findByMachineId(machineId)) {
-			stateData.add(new StateData<String, String>(s.getState(), s.isInitial()));
+			stateData.add(new StateData<String, String>(s.getParentState(), null, s.getState(), s.isInitial()));
 		}
 		StatesData<String, String> statesData = new StatesData<>(stateData);