Move LoginManager and SessionManager to the Security namespace

Signed-off-by: VirtualTam <virtualtam@flibidi.net>

tests/security/LoginManagerTest.php

@@ -1,5 +1,5 @@
 <?php
-namespace Shaarli;
+namespace Shaarli\Security;
 
 require_once 'tests/utils/FakeConfigManager.php';
 use \PHPUnit\Framework\TestCase;

tests/security/SessionManagerTest.php

@@ -5,7 +5,7 @@ require_once 'tests/utils/FakeConfigManager.php';
 require_once 'tests/utils/ReferenceSessionIdHashes.php';
 ReferenceSessionIdHashes::genAllHashes();
 
-use \Shaarli\SessionManager;
+use \Shaarli\Security\SessionManager;
 use \PHPUnit\Framework\TestCase;