Apply builder pattern to ConnectionConfiguration

Introducing a clean split between the constant connection configuration
parameters, which are now all in ConnectionConfiguration and the dynamic
connection state (e.g. hostAddresses) which are now in
AbstractXMPPConnection.

Also removed all arguments of login() since the username, password,
resource and callback handler need now to be configured via
ConnectionConfiguration.

Also remove documentation/extensions/messageevents.md, as it's already
in documentation/legacy

smack-core/src/test/java/org/jivesoftware/smack/ChatConnectionTest.java

@@ -354,7 +354,7 @@ public class ChatConnectionTest {
         
         try {
             con.connect();
-            con.login("me", "secret");
+            con.login();
         } catch (Exception e) {
             // No need for handling in a dummy connection.
         }

smack-core/src/test/java/org/jivesoftware/smack/DummyConnection.java

@@ -23,6 +23,7 @@ import java.util.concurrent.BlockingQueue;
 import java.util.concurrent.LinkedBlockingQueue;
 import java.util.concurrent.TimeUnit;
 
+import org.jivesoftware.smack.ConnectionConfiguration.ConnectionConfigurationBuilder;
 import org.jivesoftware.smack.packet.Packet;
 import org.jivesoftware.smack.packet.PlainStreamElement;
 import org.jivesoftware.smack.packet.TopLevelStreamElement;
@@ -53,8 +54,13 @@ public class DummyConnection extends AbstractXMPPConnection {
 
     private final BlockingQueue<TopLevelStreamElement> queue = new LinkedBlockingQueue<TopLevelStreamElement>();
 
+    public static ConnectionConfigurationBuilder<?,?> getDummyConfigurationBuilder() {
+        return DummyConnectionConfiguration.builder().setServiceName("example.org").setUsernameAndPassword("dummy",
+                        "dummypass");
+    }
+
     public DummyConnection() {
-	this(new ConnectionConfiguration("example.com"));
+        this(getDummyConfigurationBuilder().build());
     }
 
     public DummyConnection(ConnectionConfiguration configuration) {
@@ -63,12 +69,16 @@ public class DummyConnection extends AbstractXMPPConnection {
         for (ConnectionCreationListener listener : XMPPConnectionRegistry.getConnectionCreationListeners()) {
             listener.connectionCreated(this);
         }
-        connected = true;
-        user = "dummy@" + config.getServiceName() + "/Test";
+        user = config.getUsername()
+                        + "@"
+                        + config.getServiceName()
+                        + "/"
+                        + (config.getResource() != null ? config.getResource() : "Test");
     }
 
     @Override
     protected void connectInternal() {
+        connected = true;
         connectionID = "dummy-" + new Random(new Date().getTime()).nextInt();
 
         if (reconnect) {
@@ -130,19 +140,13 @@ public class DummyConnection extends AbstractXMPPConnection {
     }
 
     @Override
-    public void login(String username, String password, String resource)
+    protected void loginNonAnonymously()
             throws XMPPException {
-        if (!isConnected()) {
-            throw new IllegalStateException("Not connected to server.");
-        }
-        if (isAuthenticated()) {
-            throw new IllegalStateException("Already logged in to server.");
-        }
-        user = (username != null ? username : "dummy")
+        user = config.getUsername()
                 + "@"
                 + config.getServiceName()
                 + "/" 
-                + (resource != null ? resource : "Test");
+                + (config.getResource() != null ? config.getResource() : "Test");
         roster = new Roster(this);
         anonymous = false;
         authenticated = true;
@@ -226,4 +230,32 @@ public class DummyConnection extends AbstractXMPPConnection {
 
         invokePacketCollectorsAndNotifyRecvListeners(packet);
     }
+
+    public static class DummyConnectionConfiguration extends ConnectionConfiguration {
+        protected DummyConnectionConfiguration(DummyConnectionConfigurationBuilder builder) {
+            super(builder);
+        }
+
+        public static DummyConnectionConfigurationBuilder builder() {
+            return new DummyConnectionConfigurationBuilder();
+        }
+
+        public static class DummyConnectionConfigurationBuilder
+                        extends
+                        ConnectionConfigurationBuilder<DummyConnectionConfigurationBuilder, DummyConnectionConfiguration> {
+
+            private DummyConnectionConfigurationBuilder() {
+            }
+
+            @Override
+            public DummyConnectionConfiguration build() {
+                return new DummyConnectionConfiguration(this);
+            }
+
+            @Override
+            protected DummyConnectionConfigurationBuilder getThis() {
+                return this;
+            }
+        }
+    }
 }

smack-core/src/test/java/org/jivesoftware/smack/RosterTest.java

@@ -61,7 +61,7 @@ public class RosterTest {
 
         connection = new DummyConnection();
         connection.connect();
-        connection.login("rostertest", "secret");
+        connection.login();
         rosterListener = new TestRosterListener();
         connection.getRoster().addRosterListener(rosterListener);
     }

smack-core/src/test/java/org/jivesoftware/smack/RosterVersioningTest.java

@@ -26,6 +26,7 @@ import java.io.IOException;
 import java.util.Collection;
 import java.util.HashSet;
 
+import org.jivesoftware.smack.ConnectionConfiguration.ConnectionConfigurationBuilder;
 import org.jivesoftware.smack.packet.IQ;
 import org.jivesoftware.smack.packet.IQ.Type;
 import org.jivesoftware.smack.packet.Packet;
@@ -64,12 +65,12 @@ public class RosterVersioningTest {
         DirectoryRosterStore store = DirectoryRosterStore.init(tmpFolder.newFolder("store"));
         populateStore(store);
 
-        ConnectionConfiguration conf = new ConnectionConfiguration("dummy");
-        conf.setRosterStore(store);
-        connection = new DummyConnection(conf);
+        ConnectionConfigurationBuilder<?, ?> builder = DummyConnection.getDummyConfigurationBuilder();
+        builder.setRosterStore(store);
+        connection = new DummyConnection(builder.build());
         connection.connect();
 
-        connection.login("rostertest", "secret");
+        connection.login();
     }
 
     @After