Remove unused imports, raw types and some deprecated method calls..

broker/src/main/java/io/moquette/spi/persistence/MapDBPersistentStore.java

@@ -45,7 +45,8 @@ public class MapDBPersistentStore {
      * a session.
      * */
     public static class PersistentSession implements Serializable {
-        public final boolean cleanSession;
+		private static final long serialVersionUID = 1L;
+		public final boolean cleanSession;
 
         public PersistentSession(boolean cleanSession) {
             this.cleanSession = cleanSession;

broker/src/main/java/io/moquette/spi/persistence/MapDBSessionsStore.java

@@ -16,7 +16,6 @@
 package io.moquette.spi.persistence;
 
 import io.moquette.spi.ClientSession;
-import io.moquette.spi.IMessagesStore;
 import io.moquette.spi.IMessagesStore.StoredMessage;
 import io.moquette.spi.ISessionsStore;
 import io.moquette.spi.MessageGUID;