Merged topic subscription search and publish into single MessagePublisher method

First step on implementing H2 storage

Minor, fixed not imported class

Cleaned MessageStore interface to avoid duplication of methods used in couple. Switched from guid + message to move messages

Separated ISubscriptionsStore from ISessionStore

Implemented H2 queue

broker/src/test/java/io/moquette/spi/ClientSessionTest.java

@@ -18,7 +18,7 @@ package io.moquette.spi;
 
 import io.moquette.persistence.MemoryStorageService;
 import io.moquette.spi.impl.subscriptions.Subscription;
-import io.moquette.spi.impl.subscriptions.SubscriptionsStore;
+import io.moquette.spi.impl.subscriptions.SubscriptionsDirectory;
 import io.moquette.spi.impl.subscriptions.Topic;
 import static io.netty.handler.codec.mqtt.MqttQoS.*;
 import org.junit.Before;
@@ -31,11 +31,11 @@ public class ClientSessionTest {
     ClientSession session1;
     ClientSession session2;
     ISessionsStore sessionsStore;
-    SubscriptionsStore store;
+    SubscriptionsDirectory store;
 
     @Before
     public void setUp() {
-        store = new SubscriptionsStore();
+        store = new SubscriptionsDirectory();
         MemoryStorageService storageService = new MemoryStorageService();
         this.sessionsStore = storageService.sessionsStore();
         store.init(sessionsStore);