Lists related event in keyValue list.

https://github.com/BentoBoxWorld/bentobox/issues/352

Rather than overriding the existing getEventName() method for Events, I
decided to keep it as a key-value reference.

src/main/java/world/bentobox/level/calculators/PlayerLevel.java

@@ -57,6 +57,7 @@ public class PlayerLevel {
         IslandLevelCalculatedEvent ilce = new IslandLevelCalculatedEvent(targetPlayer, island, calc.getResult());
         addon.getServer().getPluginManager().callEvent(ilce);
         Map<String, Object> keyValues = new HashMap<>();
+        keyValues.put("eventName", "IslandLevelCalculatedEvent");
         keyValues.put("targetPlayer", targetPlayer);
         keyValues.put("islandUUID", island.getUniqueId());
         keyValues.put("level", calc.getResult().getLevel());