Allow enabling sand duping (#10191)

Because this exploit has been widely known for years and has not been fixed by Mojang, we decided that it was worth allowing people to toggle it on/off due to how easy it is to make it configurable.

It should be noted that this decision does not promise all future exploits will be configurable.

patches/server/0473-Additional-Block-Material-API.patch

@@ -0,0 +1,40 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Aikar <aikar@aikar.co>
+Date: Wed, 30 Dec 2020 19:43:01 -0500
+Subject: [PATCH] Additional Block Material API
+
+Faster version for isSolid() that utilizes NMS's state for isSolid instead of the slower
+process to do this in the Bukkit API
+
+Adds API for buildable, replaceable, burnable too.
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java b/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
+index aa644231425b9622437538b5c092d4064a40cced..98e87dc15e2ed23f6897ba6359846ff5bc32b655 100644
+--- a/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
++++ b/src/main/java/org/bukkit/craftbukkit/block/CraftBlock.java
+@@ -440,6 +440,25 @@ public class CraftBlock implements Block {
+         return this.getNMS().liquid();
+     }
+ 
++    // Paper start
++    @Override
++    public boolean isBuildable() {
++        return this.getNMS().isSolid(); // This is in fact isSolid, despite the fact that isSolid below returns blocksMotion
++    }
++    @Override
++    public boolean isBurnable() {
++        return this.getNMS().ignitedByLava();
++    }
++    @Override
++    public boolean isReplaceable() {
++        return this.getNMS().canBeReplaced();
++    }
++    @Override
++    public boolean isSolid() {
++        return this.getNMS().blocksMotion();
++    }
++    // Paper end
++
+     @Override
+     public PistonMoveReaction getPistonMoveReaction() {
+         return PistonMoveReaction.getById(this.getNMS().getPistonPushReaction().ordinal());