made ZapHandler library

lib/ZAPHandler.interface.php

@@ -0,0 +1,12 @@
+<?php
+/**
+ * Interface for ZAP mode handlers.
+ * All ZAP handler classes must implement this interface.
+ */
+interface ZAPHandler {
+	/**
+	 * Renders and returns the content for this mode.
+	 * @return string
+	 */
+	public function getContent();
+}