Improvements to BlockStates

* Update Javadoc of block state classes to better match implementation behaviour.
* Add Container interface which provides access to the snapshot inventory.

By: Lukas Hennig <lukas@wirsindwir.de>

paper-api/src/main/java/org/bukkit/block/EnchantingTable.java

@@ -3,6 +3,6 @@ package org.bukkit.block;
 import org.bukkit.Nameable;
 
 /**
- * Represents an enchanting table.
+ * Represents a captured state of an enchanting table.
  */
 public interface EnchantingTable extends BlockState, Nameable { }