rename events package, add aggregat superclass

src/main/java/mops/gruppen2/events/Event.java

@@ -0,0 +1,12 @@
+package mops.gruppen2.events;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+@Getter
+@AllArgsConstructor
+public class Event {
+	long id;
+	long gruppe_id;
+	long user_id;
+}