Add EXPLOSION and DEFAULT RemoveCauses to the HangingBreakEvent.

EXPLOSION is used when a hanging entity is removed by an explosion.
DEFAULT is used when a hanging entity is removed by an uncategorised
cause.

src/main/java/org/bukkit/event/hanging/HangingBreakEvent.java

@@ -42,6 +42,10 @@ public class HangingBreakEvent extends HangingEvent implements Cancellable {
          * Removed by an entity
          */
         ENTITY,
+        /**
+         * Removed by an explosion
+         */
+        EXPLOSION,
         /**
          * Removed by placing a block on it
          */
@@ -50,6 +54,10 @@ public class HangingBreakEvent extends HangingEvent implements Cancellable {
          * Removed by destroying the block behind it, etc
          */
         PHYSICS,
+        /**
+         * Removed by an uncategorised cause
+         */
+        DEFAULT,
     }
 
     @Override