Added new set/get age methods to Animals

By: Nathan Adams <dinnerbone@dinnerbone.com>

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

@@ -4,4 +4,18 @@ package org.bukkit.entity;
  * Represents an Animal.
  *
  */
-public interface Animals extends Creature {}
+public interface Animals extends Creature {
+    /**
+     * Gets the age of this animal.
+     * 
+     * @return Age
+     */
+    public int getAge();
+
+    /**
+     * Sets the age of this animal.
+     *
+     * @param age New age
+     */
+    public void setAge(int age);
+}