Per-world Creeper settings complete

- Added per-world Block Damage settings
- Added per-world Entity Damage settings
- Added creeper_settings database support
- Added world-specific Creeper menus
- Added automatic world registration/default inheritance
- Split Creeper listeners
- Updated Creeper behavior to use world settings
- Removed obsolete global Creeper indicators
- Adopted logger-based error reporting standard

src/main/java/com/rsscripting/serveradmin/menuholder/RSMenuHolder.java

@@ -0,0 +1,73 @@
+package com.rsscripting.serveradmin.menuholder;
+
+import org.bukkit.inventory.Inventory;
+import org.bukkit.inventory.InventoryHolder;
+import org.jetbrains.annotations.NotNull;
+
+public class RSMenuHolder
+        implements InventoryHolder {
+
+    private final String menuId;
+
+    private int page = 1;
+
+    private String worldName;
+
+    public RSMenuHolder(
+            String menuId
+    ) {
+
+        this.menuId = menuId;
+
+    }
+
+    public String getMenuId() {
+
+        return menuId;
+
+    }
+
+    public int getPage() {
+
+        return page;
+
+    }
+
+    public void setPage(
+            int page
+    ) {
+
+        if (page < 1) {
+
+            page = 1;
+
+        }
+
+        this.page = page;
+
+    }
+
+    public String getWorldName() {
+
+        return worldName;
+
+    }
+
+    public void setWorldName(
+            String worldName
+    ) {
+
+        this.worldName = worldName;
+
+    }
+
+    @Override
+    public @NotNull Inventory getInventory() {
+
+        throw new UnsupportedOperationException(
+                "RSMenuHolder does not store an inventory."
+        );
+
+    }
+
+}