Fix #1370

- Actually override toNative in adapter
 - Correctly assign generic-type
 - Better default method for BinaryTag retrieval in adapter

worldedit-bukkit/src/main/java/com/sk89q/worldedit/bukkit/adapter/BukkitImplAdapter.java

@@ -286,7 +286,7 @@ public interface BukkitImplAdapter<T> extends IBukkitAdapter {
     }
 
     default BinaryTag toNativeBinary(T foreign) {
-        return null;
+        return toNative(foreign).asBinaryTag();
     }
 
     @Deprecated