[Bleeding] MaterialData fixes. Addresses BUKKIT-842

By: Celtic Minstrel <celtic.minstrel.ca@some.place>

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

@@ -0,0 +1,17 @@
+package org.bukkit.material;
+
+public interface Openable {
+    /**
+     * Check to see if the door is open.
+     *
+     * @return true if the door has swung counterclockwise around its hinge.
+     */
+    boolean isOpen();
+
+    /**
+     * Configure this door to be either open or closed;
+     *
+     * @param isOpen True to open the door.
+     */
+    void setOpen(boolean isOpen);
+}