Added various new 1.9 entities, blocks and items

By: Nathan Adams <dinnerbone@dinnerbone.com>

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

@@ -0,0 +1,15 @@
+package org.bukkit.entity;
+
+import java.util.Set;
+
+/**
+ * Represents a complex living entity - one that is made up of various smaller parts
+ */
+public interface ComplexLivingEntity extends LivingEntity {
+    /**
+     * Gets a list of parts that belong to this complex entity
+     * 
+     * @return List of parts
+     */
+    public Set<ComplexEntityPart> getParts();
+}