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/Dropper.java

@@ -1,27 +1,31 @@
 package org.bukkit.block;
 
 import org.bukkit.Nameable;
-import org.bukkit.inventory.InventoryHolder;
 
 /**
- * Represents a dropper.
+ * Represents a captured state of a dropper.
  */
-public interface Dropper extends BlockState, InventoryHolder, Lockable, Nameable {
+public interface Dropper extends Container, Nameable {
 
     /**
-     * Tries to drop a randomly selected item from the Dropper's inventory,
-     * following the normal behavior of a Dropper.
+     * Tries to drop a randomly selected item from the dropper's inventory,
+     * following the normal behavior of a dropper.
      * <p>
-     * Normal behavior of a Dropper is as follows:
+     * Normal behavior of a dropper is as follows:
      * <p>
-     * If the block that the Dropper is facing is an InventoryHolder,
+     * If the block that the dropper is facing is an InventoryHolder,
      * the randomly selected ItemStack is placed within that 
      * Inventory in the first slot that's available, starting with 0 and
      * counting up.  If the inventory is full, nothing happens.
      * <p>
-     * If the block that the Dropper is facing is not an InventoryHolder,
+     * If the block that the dropper is facing is not an InventoryHolder,
      * the randomly selected ItemStack is dropped on
      * the ground in the form of an {@link org.bukkit.entity.Item Item}.
+     * <p>
+     * If the block represented by this state is no longer a dropper, this will
+     * do nothing.
+     * 
+     * @throws IllegalStateException if this block state is not placed
      */
     public void drop();
 }