Satisfy find bugs by adding Serializable

src/main/java/de/thm/arsnova/controller/CourseController.java

@@ -18,6 +18,7 @@
  */
 package de.thm.arsnova.controller;
 
+import java.io.Serializable;
 import java.util.Collections;
 import java.util.Comparator;
 import java.util.List;
@@ -71,7 +72,9 @@ public class CourseController extends AbstractController {
 		return result;
 	}
 
-	private static class CourseNameComperator implements Comparator<Course> {
+	private static class CourseNameComperator implements Comparator<Course>, Serializable {
+		private static final long serialVersionUID = 1L;
+
 		@Override
 		public int compare(Course course1, Course course2) {
 			return course1.getFullname().compareToIgnoreCase(course2.getFullname());

src/main/java/de/thm/arsnova/services/SessionService.java

@@ -19,6 +19,7 @@
 
 package de.thm.arsnova.services;
 
+import java.io.Serializable;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.Comparator;
@@ -155,7 +156,9 @@ public class SessionService implements ISessionService {
 		return databaseDao.countActiveUsers(session, since);
 	}
 	
-	public static class SessionNameComperator implements Comparator<Session> {
+	public static class SessionNameComperator implements Comparator<Session>, Serializable{
+		private static final long serialVersionUID = 1L;
+
 		@Override
 		public int compare(Session session1, Session session2) {
 			return session1.getName().compareToIgnoreCase(session2.getName());