First Changes

- Added login.php, registration.php, logout.php in root folder.
Changed Lib\authentication.php, Lib\registration.php, Lib\logout.php.
Created Lib\login.phtml.
Lib\logout.php moved  to root folder.

- In some files replaced $_SERVER['DOCUMENT_ROOT'] on __DIR__

- Config\connect.php moved to functions folder.
Deleted string $connect = getPdo(); in Functions\connect.php.
Added strings $connnect = getPdo(); in Functions\database.php.

- Deleted string session_start() in Lib\authentication.php and
Lib\registration.php.
Added string session_start() to login.php and registration.php

- Fixed regular expressions.
Changed '[.]' to '.'
Added the use of parentheses in login and password.

- Added more special symbols in salt.