Apply Some Java 8 Code Changes

* Make most functional interfaces as `@FunctionalInterface`
* Convert some abstract classes to `@FunctionalInterface` with `default` methods
* Apply Lambda style implementation in some places
* Remove `Function` in favor of similar in Java 8

*  Remove redundant code from `DefaultAmqpHeaderMapper` since we are already on Spring AMQP-2.0
* Add several ctors to the `ExpressionEvaluatingMessageListProcessor`
* Populate explicit `Boolean.class` `expectedType` from the `ExpressionEvaluatingReleaseStrategy`

spring-integration-syslog/src/main/java/org/springframework/integration/syslog/MessageConverter.java

@@ -26,6 +26,7 @@ import org.springframework.messaging.Message;
  * @since 3.0
  *
  */
+@FunctionalInterface
 public interface MessageConverter {
 
 	Message<?> fromSyslog(Message<?> syslog) throws Exception;