add missing namespaces/fix wrong class-names

doc/Addons.md

@@ -181,6 +181,8 @@ Put your tpl files in the *templates/* subfolder of your addon.
 In your code, like in the function addon_name_content(), load the template file and execute it passing needed values:
 
 ```php
+use Friendica\Core\Renderer;
+
 # load template file. first argument is the template name,
 # second is the addon path relative to friendica top folder
 $tpl = Renderer::getMarkupTemplate('mytemplate.tpl', __DIR__);

doc/autoloader.md

@@ -47,8 +47,10 @@ The code will be something like:
 // mod/network.php
 <?php
 
+use Friendica\App;
+
 function network_content(App $a) {
-	$itemsmanager = new Friendica\ItemsManager();
+	$itemsmanager = new \Friendica\ItemsManager();
 	$items = $itemsmanager->getAll();
 
 	// pass $items to template
@@ -117,6 +119,8 @@ If your code is in same namespace as the class you need, you don't need to prepe
 
 namespace Friendica;
 
+use Friendica\Protocol\DFRN;
+
 // this is the same content of current include/delivery.php,
 // but has been declared to be in "Friendica" namespace