Add definitions for Minecraft 1.9 gameplay elements

Includes an API for AreaEffectCloud and rework of Sound enum to include new sound values.

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

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

@@ -0,0 +1,34 @@
+package org.bukkit.entity;
+
+import org.bukkit.projectiles.ProjectileSource;
+
+public interface ShulkerBullet extends Entity {
+
+    /**
+     * Retrieve the shooter of this bullet.
+     *
+     * @return the {@link ProjectileSource} that shot this bullet
+     */
+    ProjectileSource getShooter();
+
+    /**
+     * Set the shooter of this bullet.
+     *
+     * @param source the {@link ProjectileSource} that shot this bullet
+     */
+    void setShooter(ProjectileSource source);
+
+    /**
+     * Retrieve the target of this bullet.
+     *
+     * @return the targeted entity
+     */
+    Entity getTarget();
+
+    /**
+     * Sets the target of this bullet
+     *
+     * @param target the entity to target
+     */
+    void setTarget(Entity target);
+}