Added the UserStatusChangeProcessor and its implementation

this commit serves as solution to the merge conflict between
f/user_status_change_processor and develop

src/main/java/envoy/client/net/Client.java

@@ -14,9 +14,7 @@ import envoy.client.data.Config;
 import envoy.client.data.LocalDb;
 import envoy.client.util.EnvoyLog;
 import envoy.data.*;
-import envoy.event.Event;
-import envoy.event.IdGeneratorRequest;
-import envoy.event.MessageStatusChangeEvent;
+import envoy.event.*;
 import envoy.util.SerializationUtils;
 
 /**
@@ -100,6 +98,8 @@ public class Client implements Closeable {
 		receiver.removeAllProcessors();
 
 		// Register processors for message and status handling
+
+		// Process incoming messages
 		final ReceivedMessageProcessor receivedMessageProcessor = new ReceivedMessageProcessor();
 		receiver.registerProcessor(Message.class, receivedMessageProcessor);
 
@@ -109,6 +109,9 @@ public class Client implements Closeable {
 		// Process message status changes
 		receiver.registerProcessor(MessageStatusChangeEvent.class, new MessageStatusChangeEventProcessor());
 
+		// Process user status changes
+		receiver.registerProcessor(UserStatusChangeEvent.class, new UserStatusChangeProcessor(this));
+
 		// Process message ID generation
 		receiver.registerProcessor(IdGenerator.class, localDb::setIdGenerator);
 
@@ -207,4 +210,16 @@ public class Client implements Closeable {
 	 * @since Envoy v0.2-alpha
 	 */
 	public boolean isOnline() { return online; }
+
+	/**
+	 * @return the contacts of this {@link Client}
+	 * @since Envoy v0.3-alpha
+	 */
+	public Contacts getContacts() { return contacts; }
+
+	/**
+	 * @param contacts the contacts to set
+	 * @since Envoy v0.3-alpha
+	 */
+	public void setContacts(Contacts contacts) { this.contacts = contacts; }
 }