Fix bugs with pistons

This commit improves piston tracking and fixes a couple of bugs with
block tracking.

Fixes #2043

src/main/java/com/gmail/nossr50/util/BlockUtils.java

@@ -308,6 +308,12 @@ public final class BlockUtils {
         return type == Repair.anvilMaterial || type == Salvage.anvilMaterial;
     }
 
+    public static boolean isPistonPiece(BlockState blockState) {
+        Material type = blockState.getType();
+
+        return type == Material.PISTON_MOVING_PIECE || type == Material.AIR;
+    }
+
     /**
      * Get a HashSet containing every transparent block
      *