Update to Minecraft 1.13-pre7

By: md_5 <git@md-5.net>

paper-api/src/main/java/org/bukkit/entity/Minecart.java

@@ -1,6 +1,7 @@
 package org.bukkit.entity;
 
 import org.bukkit.Material;
+import org.bukkit.block.data.BlockData;
 import org.bukkit.material.MaterialData;
 import org.bukkit.util.Vector;
 
@@ -108,6 +109,22 @@ public interface Minecart extends Vehicle {
      */
     public MaterialData getDisplayBlock();
 
+    /**
+     * Sets the display block for this minecart.
+     * Passing a null value will set the minecart to have no display block.
+     *
+     * @param blockData the material to set as display block.
+     */
+    public void setDisplayBlockData(BlockData blockData);
+
+    /**
+     * Gets the display block for this minecart.
+     * This function will return the type AIR if none is set.
+     *
+     * @return the block displayed by this minecart.
+     */
+    public BlockData getDisplayBlockData();
+
     /**
      * Sets the offset of the display block.
      *