Separated persistence layer, created submodule for MapDB persistence letting the broker use the in-memory message store

broker/src/test/java/io/moquette/server/ServerRestartIntegrationTest.java

@@ -64,7 +64,6 @@ public class ServerRestartIntegrationTest {
     @Before
     public void setUp() throws Exception {
         String dbPath = IntegrationUtils.localMapDBPath();
-        IntegrationUtils.cleanPersistenceFile(dbPath);
         startServer();
 
         m_subscriber = new MqttClient("tcp://localhost:1883", "Subscriber", s_dataStore);
@@ -85,7 +84,6 @@ public class ServerRestartIntegrationTest {
         }
 
         m_server.stopServer();
-        IntegrationUtils.cleanPersistenceFile(m_config);
     }
 
     @Test
@@ -97,7 +95,6 @@ public class ServerRestartIntegrationTest {
 
         // shutdown the server
         m_server.stopServer();
-        IntegrationUtils.cleanPersistenceFile(m_config);
 
         // restart the server
         m_server.startServer(IntegrationUtils.prepareTestProperties());