Legacy cotent-type changes for the consumer

- Remove binding config property `legacyContentTypeHeaderEnabled` that was
  introduced to enable legacy content type handling
- Enable LegacyContentTypeInterceptor in 2.0 always, but bypass any
  legacy content type handling if the message received is from
  a 2.0 producer by checking on the version header
- Introdce a new BinderHeader property for version
- Fix the LegacyContentType related tests
- Remove the check for originalContentType in ReceivingHandler when
  the payload received is a byte[]
- Remove unnecessary deserializePayloadIfNecessary calls in ReceivingHandler
- Remove deprecated deserializePayload methods in AbstractBinder
  and MessageSerializationUtils

Partly fixes #1106
Fixes #1110

spring-cloud-stream-integration-tests/src/test/java/org/springframework/cloud/stream/config/LegacyContentTypeTests.java

@@ -28,7 +28,6 @@ import org.springframework.boot.test.context.SpringBootTest;
 import org.springframework.cloud.stream.annotation.EnableBinding;
 import org.springframework.cloud.stream.binder.BinderHeaders;
 import org.springframework.cloud.stream.messaging.Sink;
-import org.springframework.context.annotation.PropertySource;
 import org.springframework.integration.support.MessageBuilder;
 import org.springframework.messaging.Message;
 import org.springframework.messaging.MessageHandler;
@@ -61,14 +60,16 @@ public class LegacyContentTypeTests {
 			}
 		};
 		testSink.input().subscribe(messageHandler);
-		testSink.input().send(MessageBuilder.withPayload("{\"message\":\"Hi\"}".getBytes()).setHeader(BinderHeaders.BINDER_ORIGINAL_CONTENT_TYPE, "application/json").build());
+		testSink.input().send(MessageBuilder.withPayload("{\"message\":\"Hi\"}".getBytes())
+							.setHeader(BinderHeaders.BINDER_ORIGINAL_CONTENT_TYPE, "application/json")
+							.setHeader(BinderHeaders.SCST_VERSION, "1.x")
+							.build());
 		assertThat(latch.await(10, TimeUnit.SECONDS)).isTrue();
 		testSink.input().unsubscribe(messageHandler);
 	}
 
 	@EnableBinding(Sink.class)
 	@EnableAutoConfiguration
-	@PropertySource("classpath:/org/springframework/cloud/stream/config/channel/legacy-sink-channel-configurers.properties")
 	public static class LegacyTestSink {
 
 	}

spring-cloud-stream-integration-tests/src/test/resources/org/springframework/cloud/stream/config/channel/legacy-sink-channel-configurers.properties

@@ -1,4 +0,0 @@
-spring.cloud.stream.bindings.input.destination=configure1
-spring.cloud.stream.bindings.input.legacyContentTypeHeaderEnabled=true
-spring.cloud.stream.bindings.input.contentType=application/x-spring-tuple
-