Add generic error handling to BasicErrorController

Since Spring supports gobal error handling through
@ControllerAdvice, it is quite easy to set up more meta-data
about an exception for the BasicErrorController. You need
to be careful not to swallow Security exceptions, and probably
others (optionally) so this feature needs a bit more work.

See gh-538

spring-boot-samples/spring-boot-sample-actuator/pom.xml

@@ -35,6 +35,10 @@
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-remote-shell</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>org.hibernate</groupId>
+			<artifactId>hibernate-validator</artifactId>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-test</artifactId>
@@ -44,6 +48,10 @@
 			<exclusions> <exclusion> <groupId>log4j</groupId> <artifactId>log4j</artifactId>
 			</exclusion> <exclusion> <groupId>commons-logging</groupId> <artifactId>commons-logging</artifactId>
 			</exclusion> </exclusions> </dependency> -->
+		<dependency>
+			<groupId>org.hibernate</groupId>
+			<artifactId>hibernate-validator</artifactId>
+		</dependency>
 	</dependencies>
 	<build>
 		<plugins>