Allow anonymous access to devtools remote server

Previously, if an app had Spring Security on the classpath the remote
devtools server would be secured using basic authentication. This
prevented RemoteSpringApplication from uploading changes to the server
as they would be rejected with a 401.

This commit updates RemoteDevToolsAutoConfiguration to allow anonymous
access to the remote server. CSRF protection is also disabled so that
POST requests without a CSRF token will be accepted.

Closes gh-3889

spring-boot-devtools/pom.xml

@@ -35,6 +35,16 @@
 			<artifactId>spring-web</artifactId>
 			<optional>true</optional>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework.security</groupId>
+			<artifactId>spring-security-config</artifactId>
+			<optional>true</optional>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.security</groupId>
+			<artifactId>spring-security-web</artifactId>
+			<optional>true</optional>
+		</dependency>
 		<dependency>
 			<groupId>javax.servlet</groupId>
 			<artifactId>javax.servlet-api</artifactId>