Move ITemplateEngine to src

- Fix method name format

src/App.php

@@ -295,7 +295,7 @@ class App {
 		// Register template engines
 		$dc = get_declared_classes();
 		foreach ($dc as $k) {
-			if (in_array('ITemplateEngine', class_implements($k))) {
+			if (in_array('Friendica\Render\ITemplateEngine', class_implements($k))) {
 				$this->register_template_engine($k);
 			}
 		}

src/Render/ITemplateEngine.php

@@ -0,0 +1,15 @@
+<?php
+/**
+ * @file src/Render/ITemplateEngine.php
+ */
+
+namespace Friendica\Render;
+
+/**
+ * Interface for template engines
+ */
+interface ITemplateEngine
+{
+	public function replaceMacros($s, $v);
+	public function getTemplateFile($file, $root = '');
+}