Added Attachable MaterialData

By: Dinnerbone <dinnerbone@dinnerbone.com>

paper-api/src/main/java/org/bukkit/material/Attachable.java

@@ -0,0 +1,16 @@
+
+package org.bukkit.material;
+
+import org.bukkit.BlockFace;
+
+/**
+ * Indicates that a block can be attached to another block
+ */
+public interface Attachable {
+    /**
+     * Gets the face that this block is attached on
+     *
+     * @return BlockFace attached to
+     */
+    public BlockFace getAttachedFace();
+}