Add per-arena setting monster-teleporting.

This setting allows server owners to allow arena monsters to teleport
around _while inside the region_. They still can't teleport out of the
region.

Taken at face value, this should just be the default behavior. However,
due to arena regions being boxes, any non-box shaped arena will need a
region that covers more than the physical arena structure, which means
mobs like Endermen will be able to teleport into possibly unreachable
areas of the physical structure. So we have to make do with a setting.

Closes #762

src/main/java/com/garbagemule/MobArena/ArenaListener.java

@@ -121,6 +121,7 @@ public class ArenaListener
     private boolean lockFoodLevel;
     private boolean useClassChests;
     private boolean allowTeleport;
+    private boolean monsterTeleport;
     private boolean canShare;
     private boolean autoIgniteTNT;
     private int autoIgniteFuse;
@@ -145,6 +146,7 @@ public class ArenaListener
         this.foodRegen        = s.getBoolean("food-regen",           false);
         this.lockFoodLevel    = s.getBoolean("lock-food-level",      true);
         this.allowTeleport    = s.getBoolean("allow-teleporting",    false);
+        this.monsterTeleport  = s.getBoolean("monster-teleporting",  false);
         this.canShare         = s.getBoolean("share-items-in-arena", true);
         this.autoIgniteTNT    = s.getBoolean("auto-ignite-tnt",      false);
         this.autoIgniteFuse   = s.getInt("auto-ignite-fuse",         80);
@@ -893,6 +895,14 @@ public class ArenaListener
         if (monsters.hasPet(event.getEntity()) && region.contains(event.getTo())) {
             return;
         }
+
+        if (isArenaMonster(event.getEntity())) {
+            if (!monsterTeleport || !region.contains(event.getTo())) {
+                event.setCancelled(true);
+            }
+            return;
+        }
+
         if (region.contains(event.getFrom()) || region.contains(event.getTo())) {
             event.setCancelled(true);
         }