Add -w flag to butcher for water mobs

beb784e0ffe1d8a8cf678912dbd6207e96afcfc8

Co-Authored-By: Lewis B <17665267+lewisjb@users.noreply.github.com>

worldedit-core/src/main/java/com/sk89q/worldedit/entity/metadata/EntityProperties.java

@@ -161,4 +161,11 @@ public interface EntityProperties {
      * @return true if pasteable
      */
     boolean isPasteable();
+
+    /**
+     * Test whether the entity is a water creature.
+     *
+     * @return true if water creature
+     */
+    boolean isWaterCreature();
 }