added missing comments and modify existing comments

* `classes/arr.php`
  * modified existing comments
* `classes/crypt.php`
  * modified existing comments
* `classes/database/mysql/connection.php`
  * added missing comments
* `classes/database/mysqli/connection.php`
  * added missing comments
* `classes/dbutil.php`
  * added missing comments
  * modified comment spacing, from tab to space
* `classes/router.php`
  * added missing comments
  * modified comment spacing, from tab to space