Added per world PVP setting support.

By: Rigby <rigby@onarandombox.com>

paper-api/src/main/java/org/bukkit/World.java

@@ -496,6 +496,18 @@ public interface World {
      */
     public long getSeed();
 
+    /**
+     * Gets the current PVP setting for this world.
+     * @return
+     */
+    public boolean getPVP();
+
+    /**
+     * Sets the PVP setting for this world.
+     * @param pvp True/False whether PVP should be Enabled.
+     */
+    public void setPVP(boolean pvp);
+
     /**
      * Saves world to disk
      */