DATAGRAPH-340 - Added shutdown() method to GraphDatabase interface.

Original pull request: #133.

spring-data-neo4j/src/main/java/org/springframework/data/neo4j/core/GraphDatabase.java

@@ -131,4 +131,6 @@ public interface GraphDatabase {
     TransactionManager getTransactionManager();
 
     Transaction beginTx();
+
+    void shutdown();
 }

spring-data-neo4j/src/main/java/org/springframework/data/neo4j/support/DelegatingGraphDatabase.java

@@ -263,6 +263,7 @@ public class DelegatingGraphDatabase implements GraphDatabase {
         return resultConverter;
     }
 
+    @Override
     public void shutdown() {
         delegate.shutdown();
     }