Session: centralise how session tokens are handled

controllers/Logout.php

@@ -11,7 +11,7 @@ class Logout extends HTMLController
 	public function __construct()
 	{
 		// Clear the entire sesssion.
-		$_SESSION = [];
+		Session::clear();
 
 		// Back to the frontpage you go.
 		header('Location: ' . BASEURL);