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/Server.java

@@ -28,6 +28,8 @@ import org.bukkit.plugin.messaging.PluginMessageRecipient;
 import org.bukkit.scheduler.BukkitScheduler;
 
 import com.avaje.ebean.config.ServerConfig;
+import org.bukkit.inventory.ItemFactory;
+import org.bukkit.inventory.meta.ItemMeta;
 
 /**
  * Represents a server implementation
@@ -679,4 +681,12 @@ public interface Server extends PluginMessageRecipient {
      * @return The configured WarningState
      */
     public WarningState getWarningState();
+
+    /**
+     * Gets the instance of the item factory (for {@link ItemMeta}).
+     *
+     * @return the item factory
+     * @see ItemFactory
+     */
+    ItemFactory getItemFactory();
 }