Add ItemMeta factory and interfaces. This adds BUKKIT-15

Included with ItemMeta is a new serializable class Color.

PotionEffects are now serializable.

By: Wesley Wolfe <weswolf@aol.com>

paper-api/src/main/java/org/bukkit/Utility.java

@@ -0,0 +1,15 @@
+package org.bukkit;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * This annotation indicates a method (and sometimes constructor) will chain its internal operations.
+ * This is solely meant for identifying methods that don't need to be overridden / handled manually.
+ */
+@Target({ElementType.CONSTRUCTOR, ElementType.METHOD})
+@Retention(RetentionPolicy.SOURCE)
+public @interface Utility {
+}