[Bleeding] Add ProjectileSource interface. Addresses BUKKIT-1038, BUKKIT-1156

By: t00thpick1 <t00thpick1dirko@gmail.com>

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

@@ -1,14 +1,25 @@
 package org.bukkit.block;
 
+import org.bukkit.projectiles.BlockProjectileSource;
+
 /**
  * Represents a dispenser.
  */
 public interface Dispenser extends BlockState, ContainerBlock {
 
     /**
-     * Attempts to dispense the contents of this block
+     * Gets the BlockProjectileSource object for this dispenser.
      * <p>
-     * If the block is no longer a dispenser, this will return false
+     * If the block is no longer a dispenser, this will return null.
+     *
+     * @return a BlockProjectileSource if valid, otherwise null
+     */
+    public BlockProjectileSource getBlockProjectileSource();
+
+    /**
+     * Attempts to dispense the contents of this block.
+     * <p>
+     * If the block is no longer a dispenser, this will return false.
      *
      * @return true if successful, otherwise false
      */