Modifies the serialVersionUID so SamplePlanner.dat can load

Fixes #105

src/Model/Activity.java

@@ -40,7 +40,7 @@
  */
 public class Activity extends Event {
 
-	private static final long serialVersionUID = 1L;
+	private static final long serialVersionUID = -486727251420646703L;
 
 	private ArrayList<Task> taskList = new ArrayList<>();
 	private int activityQuantity;

src/Model/Event.java

@@ -34,7 +34,7 @@
  */
 public class Event extends VersionControlEntity {
 
-	private static final long serialVersionUID = 1L;
+	private static final long serialVersionUID = 4940549364156632405L;
 
 	private static final int DEFAULT_DURATION = 0;
 	private static Pattern dateRegex =

src/Model/ExamEvent.java

@@ -30,7 +30,7 @@
  */
 public class ExamEvent extends Event {
 
-	private static final long serialVersionUID = 1L;
+	private static final long serialVersionUID = 1127426583437715164L;
 
 	private Room room;
 

src/Model/Task.java

@@ -39,6 +39,7 @@
  */
 public class Task extends ModelEntity {
 	// private data
+	private static final long serialVersionUID = 5768237547422537188L;
 	private ArrayList<Task> dependencies = new ArrayList<>();
 	private Deadline deadline;
 	private ArrayList<Requirement> requirements = new ArrayList<>();

src/Model/TimetableEvent.java

@@ -29,7 +29,7 @@
  */
 public class TimetableEvent extends Event {
 
-	private static final long serialVersionUID = 1L;
+	private static final long serialVersionUID = 939793921119553866L;
 
 	private Room room;
 	private Person lecturer;