Apply animal sniffer to entire build

Move animal sniffer configuration out of spring-boot-dependencies to
spring-boot-parent and apply it to all projects.

See gh-716

spring-boot-actuator/pom.xml

@@ -201,12 +201,4 @@
 			<scope>test</scope>
 		</dependency>
 	</dependencies>
-	<build>
-		<plugins>
-			<plugin>
-				<groupId>org.codehaus.mojo</groupId>
-				<artifactId>animal-sniffer-maven-plugin</artifactId>
-			</plugin>
-		</plugins>
-	</build>
 </project>