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/main/java/io/moquette/spi/IMessagesStore.java

@@ -93,16 +93,6 @@ public interface IMessagesStore {
      */
     void initStore();
 
-    /**
-     * Persist the message. If the message is empty then the topic is cleaned, else it's stored.
-     *
-     * @param topic
-     *            for the retained.
-     * @param guid
-     *            of the message to mark as retained.
-     */
-    void storeRetained(Topic topic, MessageGUID guid);
-
     /**
      * Return a list of retained messages that satisfy the condition.
      *
@@ -112,18 +102,7 @@ public interface IMessagesStore {
      */
     Collection<StoredMessage> searchMatching(IMatchingCondition condition);
 
-    /**
-     * Persist the message.
-     *
-     * @param storedMessage
-     *            the message to store for future usage.
-     * @return the unique id in the storage (guid).
-     */
-    MessageGUID storePublishForFuture(StoredMessage storedMessage);
-
-    void dropInFlightMessagesInSession(Collection<MessageGUID> pendingAckMessages);
-
-    StoredMessage getMessageByGuid(MessageGUID guid);
-
     void cleanRetained(Topic topic);
+
+    void storeRetained(Topic topic, StoredMessage storedMessage);
 }