Added new API method to McMMOPlayerLevelUpEvent to set levels gained

Closes #352

Changelog.txt

@@ -8,6 +8,7 @@ Key:
   - Removal
   
 Version 1.4.06-dev
+ + Added new API method to McMMOPlayerLevelUpEvent to set levels gained
  + Added new permission node for /ptp; mcmmo.commands.ptp.send (enabled by default)
  = Fixed displaying partial names when trying to use /ptp
  ! Changed Chimaera Wing's recipe result to use the ingredient Material

src/main/java/com/gmail/nossr50/events/experience/McMMOPlayerLevelUpEvent.java

@@ -17,6 +17,14 @@ public class McMMOPlayerLevelUpEvent extends McMMOPlayerExperienceEvent {
 
     public McMMOPlayerLevelUpEvent(Player player, SkillType skill, int levelsGained) {
         super(player, skill);
+        this.setLevelsGained(levelsGained);
+    }
+
+    /**
+     * @param levelsGained 
+     * @return Set the number of levels gained in this event
+     */
+    public void setLevelsGained(int levelsGained) {
         this.levelsGained = levelsGained;
     }