Synchronisation API and related refactorings / improvements

-> lets you synchronize with the Bitmessage network without staying connected

networking/src/main/java/ch/dissem/bitmessage/networking/Connection.java

@@ -310,6 +310,8 @@ public class Connection implements Runnable {
                 try {
                     LOG.debug("Received object " + objectMessage.getInventoryVector());
                     security().checkProofOfWork(objectMessage, ctx.getNetworkNonceTrialsPerByte(), ctx.getNetworkExtraBytes());
+                    if (ctx.getInventory().contains(objectMessage))
+                        break;
                     listener.receive(objectMessage);
                     ctx.getInventory().storeObject(objectMessage);
                     // offer object to some random nodes so it gets distributed throughout the network:

networking/src/test/java/ch/dissem/bitmessage/networking/NetworkHandlerTest.java

@@ -55,8 +55,9 @@ public class NetworkHandlerTest {
                 .nodeRegistry(new TestNodeRegistry())
                 .networkHandler(new DefaultNetworkHandler())
                 .security(new BouncySecurity())
+                .listener(Mockito.mock(BitmessageContext.Listener.class))
                 .build();
-        peer.startup(Mockito.mock(BitmessageContext.Listener.class));
+        peer.startup();
 
         nodeInventory = new TestInventory();
         networkHandler = new DefaultNetworkHandler();
@@ -68,13 +69,14 @@ public class NetworkHandlerTest {
                 .nodeRegistry(new TestNodeRegistry(localhost))
                 .networkHandler(networkHandler)
                 .security(new BouncySecurity())
+                .listener(Mockito.mock(BitmessageContext.Listener.class))
                 .build();
     }
 
     @Test(timeout = 20_000)
     public void ensureNodesAreConnecting() {
         try {
-            node.startup(Mockito.mock(BitmessageContext.Listener.class));
+            node.startup();
             Property status;
             do {
                 Thread.yield();

networking/src/test/java/ch/dissem/bitmessage/networking/TestInventory.java

@@ -60,6 +60,11 @@ public class TestInventory implements Inventory {
         inventory.put(object.getInventoryVector(), object);
     }
 
+    @Override
+    public boolean contains(ObjectMessage object) {
+        return inventory.containsKey(object.getInventoryVector());
+    }
+
     @Override
     public void cleanup() {