broker/MapDBPersistentStore: Interfaces used for the Constructors

broker/IStore: Interface added for MapDBPersistentStore
broker/ProtocolProcessorBootstrapper: class loader for store added
broker/ISessionsStore#mapToGuid: moved to IMessagesStore
broker/ProtocolProcessorBootstrapper: getter used for SessionStore
broker/Server: getter for processor added
broker/ProtocolProcessor: getter added for Stores

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

@@ -22,7 +22,6 @@ public class ClientSessionTest {
     public void setUp() {
         store = new SubscriptionsStore();
         MemoryStorageService storageService = new MemoryStorageService();
-        storageService.initStore();
         this.sessionsStore = storageService.sessionsStore();
         store.init(sessionsStore);