Add disable if MV is used

Author: tastybento

src/main/java/world/bentobox/boxed/Boxed.java

@@ -131,6 +131,11 @@ public void onEnable() {
         if (this.getPlugin().getAddonsManager().getAddonByName("InvSwitcher").isEmpty()) {
             this.logWarning("Boxed normally requires the InvSwitcher addon for per-world Advancements.");
         }
+        if (Bukkit.getPluginManager().isPluginEnabled("MultiverseCore")) {
+            this.logError("Boxed is not compatible with Multiverse! Disabling!");
+            this.setState(State.DISABLED);
+            return;
+        }
         // Advancements manager
         advManager = new AdvancementsManager(this);
         // Make flags only applicable to this game mode