spring-rest-shell (#2928)

* code snippets for the `Java 9 Stream API improvements` article

* code snippets for the `Java 9 Stream API improvements` article [2 attempt]

* removed the first attempt

* the Spring 5 WebClient

* delted stream features test

* HttpMediaTypeNotAcceptableExceptionExampleController [0]

* reactive web client service was removed

* new WebClient

* new WebClient [2]

* spring-rest-shell init

* pom added

* readme added

spring-rest-shell/src/main/java/com/baeldung/Application.java

@@ -0,0 +1,13 @@
+package com.baeldung;
+
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class Application {
+
+    public static void main(String[] args) {
+        SpringApplication.run(Application.class, args);
+    }
+
+}