Refactor namespaces

- Remove unused use statements
- Add required use statements
- Escape global classes

src/Core/Theme.php

@@ -7,10 +7,10 @@
 namespace Friendica\Core;
 
 use Friendica\BaseObject;
-use Friendica\Core\Logger;
-use Friendica\Core\System;
 use Friendica\Model\Profile;
 
+require_once 'boot.php';
+
 /**
  * Some functions to handle themes
  */