Initial implementation of multibinder support

- Addresses #138,#172,#173 with support for multiple binders in an application
- Binders can be of multiple types (e.g. Rabbit or Kafka), as well as multiple binders of the same type connecting to different system (e.g. multiple Rabbit binders connecting to different Rabbit clusters)
- Binders are now created in a separate context, allowing for multiple configurations
- Adds the `spring.cloud.spring.binders` namespace that allows for creating configuration properties for multiple binders
- Add support for default binder, modify Kafka tests to use multiple brokers when running embedded

spring-cloud-stream-samples/multibinder-differentsystems/src/main/java/multibinder/BridgeTransformer.java

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+/*
+ * Copyright 2015 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package multibinder;
+
+import org.springframework.cloud.stream.annotation.EnableBinding;
+import org.springframework.cloud.stream.messaging.Processor;
+import org.springframework.integration.annotation.ServiceActivator;
+
+/**
+ * @author Marius Bogoevici
+ */
+@EnableBinding(Processor.class)
+public class BridgeTransformer {
+
+	@ServiceActivator(inputChannel = Processor.INPUT, outputChannel = Processor.OUTPUT)
+	public Object transform(Object payload) {
+		return payload;
+	}
+}

spring-cloud-stream-samples/multibinder-differentsystems/src/main/java/multibinder/MultibinderApplication.java

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+/*
+ * Copyright 2015 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package multibinder;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class MultibinderApplication {
+
+	public static void main(String[] args) {
+		SpringApplication.run(MultibinderApplication.class, args);
+	}
+
+}

spring-cloud-stream-samples/multibinder-differentsystems/src/main/resources/application.yml

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+server:
+  port: 8082
+spring:
+  cloud:
+    stream:
+      bindings:
+        input:
+          destination: dataIn
+          binder: kafka1
+        output:
+          destination: dataOut
+          binder: kafka2
+      binders:
+        kafka1:
+         type: kafka
+         environment:
+           spring:
+             cloud:
+               stream:
+                binder:
+                  kafka:
+                    brokers: ${kafkaBroker1}
+                    zkNodes: ${zk1}
+        kafka2:
+         type: kafka
+         environment:
+           spring:
+             cloud:
+               stream:
+                 binder:
+                   kafka:
+                     brokers: ${kafkaBroker2}
+                     zkNodes: ${zk2}

spring-cloud-stream-samples/multibinder-differentsystems/src/test/java/multibinder/TwoKafkaBindersApplicationTest.java

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+/*
+ * Copyright 2015 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package multibinder;
+
+import java.util.UUID;
+
+import org.hamcrest.CoreMatchers;
+import org.hamcrest.Matchers;
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.SpringApplicationConfiguration;
+import org.springframework.cloud.stream.binder.BinderFactory;
+import org.springframework.cloud.stream.test.junit.kafka.KafkaTestSupport;
+import org.springframework.cloud.stream.test.junit.redis.RedisTestSupport;
+import org.springframework.integration.channel.DirectChannel;
+import org.springframework.integration.channel.QueueChannel;
+import org.springframework.messaging.Message;
+import org.springframework.messaging.MessageChannel;
+import org.springframework.messaging.support.MessageBuilder;
+import org.springframework.test.annotation.DirtiesContext;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+import org.springframework.test.context.web.WebAppConfiguration;
+
+@RunWith(SpringJUnit4ClassRunner.class)
+@SpringApplicationConfiguration(classes = MultibinderApplication.class)
+@WebAppConfiguration
+@DirtiesContext
+public class TwoKafkaBindersApplicationTest {
+
+	@ClassRule
+	public static KafkaTestSupport kafkaTestSupport1 = new KafkaTestSupport();
+
+	@ClassRule
+	public static KafkaTestSupport kafkaTestSupport2 = new KafkaTestSupport();
+
+	@ClassRule
+	public static RedisTestSupport redisTestSupport = new RedisTestSupport();
+
+	@BeforeClass
+	public static void setupEnvironment() {
+		System.setProperty("kafkaBroker1", kafkaTestSupport1.getBrokerAddress());
+		System.setProperty("zk1", kafkaTestSupport1.getZkConnectString());
+		System.setProperty("kafkaBroker2", kafkaTestSupport2.getBrokerAddress());
+		System.setProperty("zk2", kafkaTestSupport2.getZkConnectString());
+	}
+
+	@Autowired
+	private BinderFactory<MessageChannel> binderFactory;
+
+	@Test
+	public void contextLoads() {
+	}
+
+	@Test
+	public void messagingWorks() {
+		DirectChannel dataProducer = new DirectChannel();
+		binderFactory.getBinder("kafka1").bindProducer("dataIn", dataProducer, null);
+
+		QueueChannel dataConsumer = new QueueChannel();
+		binderFactory.getBinder("kafka2").bindPubSubConsumer("dataOut", dataConsumer,
+				UUID.randomUUID().toString(), null);
+
+		String testPayload = "testFoo" + UUID.randomUUID().toString();
+		dataProducer.send(MessageBuilder.withPayload(testPayload).build());
+
+		Message<?> receive = dataConsumer.receive(2000);
+		Assert.assertThat(receive, Matchers.notNullValue());
+		Assert.assertThat(receive.getPayload(), CoreMatchers.equalTo(testPayload));
+	}
+
+}