Move port config to application.properties

Author: jkutner

Procfile

@@ -1 +1 @@
-web: java $JAVA_OPTS -Dserver.port=$PORT -jar target/java-getting-started-1.0.jar
+web: java -jar target/java-getting-started-1.0.jar

src/main/resources/application.properties

@@ -7,3 +7,5 @@ spring.thymeleaf.mode=HTML
 logging.level.org.springframework=INFO
 
 spring.profiles.active=production
+
+server.port=${PORT}