Add BlockStateMeta which allows creating and editting 1.8's blockEntityTag

By: Thinkofdeath <thinkofdeath@spigotmc.org>

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

@@ -192,4 +192,15 @@ public interface BlockState extends Metadatable {
      */
     @Deprecated
     public void setRawData(byte data);
+
+    /**
+     * Returns whether this state is placed in the world.
+     *
+     * Some methods will not work if the blockState isn't
+     * placed in the world.
+     *
+     * @return whether the state is placed in the world
+     *         or 'virtual' (e.g. on an itemstack)
+     */
+    boolean isPlaced();
 }

paper-api/src/main/java/org/bukkit/inventory/meta/BlockStateMeta.java

@@ -0,0 +1,35 @@
+
+package org.bukkit.inventory.meta;
+
+import org.bukkit.block.BlockState;
+
+public interface BlockStateMeta extends ItemMeta {
+
+    /**
+     * Returns whether the item has a block state currently
+     * attached to it.
+     * 
+     * @return whether a block state is already attached
+     */
+    boolean hasBlockState();
+
+    /**
+     * Returns the currently attached block state for this
+     * item or creates a new one if one doesn't exist.
+     *
+     * The state is a copy, it must be set back (or to another
+     * item) with {@link #setBlockState(org.bukkit.block.BlockState)}
+     *
+     * @return the attached state or a new state
+     */
+    BlockState getBlockState();
+
+    /**
+     * Attaches a copy of the passed block state to the item.
+     *
+     * @param blockState the block state to attach to the block.
+     * @throws IllegalArgumentException if the blockState is null
+     *         or invalid for this item.
+     */
+    void setBlockState(BlockState blockState);
+}