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/Chest.java

@@ -2,18 +2,25 @@ package org.bukkit.block;
 
 import org.bukkit.Nameable;
 import org.bukkit.inventory.Inventory;
-import org.bukkit.inventory.InventoryHolder;
 
 /**
- * Represents a chest.
+ * Represents a captured state of a chest.
  */
-public interface Chest extends BlockState, InventoryHolder, Lockable, Nameable {
+public interface Chest extends Container, Nameable {
 
     /**
-     * Returns the chest's inventory. If this is a double chest, it returns
-     * just the portion of the inventory linked to this half of the chest.
+     * Gets the inventory of the chest block represented by this block state.
+     * <p>
+     * If the chest is a double chest, it returns just the portion of the
+     * inventory linked to the half of the chest corresponding to this block state.
+     * <p>
+     * If the block was changed to a different type in the meantime, the
+     * returned inventory might no longer be valid.
+     * <p>
+     * If this block state is not placed this will return the captured
+     * inventory snapshot instead.
      *
-     * @return The inventory.
+     * @return the inventory
      */
     Inventory getBlockInventory();
 }