Fix ignore-if-block-in-hand issue with empty hand counting as a air block

Replace Timers with Bukkit schedulers
Some refactoring optimizations
Add quartz stairs to default config

src/config.yml

@@ -25,6 +25,7 @@ allowed-blocks:
     - BRICK_STAIRS
     - SMOOTH_STAIRS
     - NETHER_BRICK_STAIRS
+    - QUARTZ_STAIRS
 valid-signs:
   - SIGN
   - WALL_SIGN