GH-698 Fix routing function support in AWS

Introduce auto-fallback to routing function if more then one function is present and no definition is provided.
Add explicit routing sample

Add documentation

spring-cloud-function-samples/function-sample-aws-routing/src/main/java/example/FunctionConfiguration.java

@@ -0,0 +1,29 @@
+package example;
+
+import java.util.function.Function;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.annotation.Bean;
+
+@SpringBootApplication
+public class FunctionConfiguration {
+
+	/*
+	 * You need this main method or explicit <start-class>example.FunctionConfiguration</start-class>
+	 * in the POM to ensure boot plug-in makes the correct entry
+	 */
+	public static void main(String[] args) {
+		SpringApplication.run(FunctionConfiguration.class, args);
+	}
+
+	@Bean
+	public Function<String, String> uppercase() {
+		return value -> value.toUpperCase();
+	}
+
+	@Bean
+	public Function<String, String> reverse() {
+		return value -> new StringBuilder(value).reverse().toString();
+	}
+}