Write core classes

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Core classes to handle specific requirements:

• Database Query Builder : initially only MySQL (db.php) : PDO
• Page Generator : template engine, language manager, resource includer (page.php)
• HTML Code Generator: Independent elements, form elements
• Time Handler (local, server, UTC) (clock.php)
• User Management : admin, guest and all users - session, account, permissions (user.php)
• File Management : file reader, writer, cache, cookie (file.php)
• Log Management : admin, guest and all users (log.php)
• User Input Management : settings, posts, any kind of form interaction (input.php)
• Error Management : all kind of friendly error message generator - reporting to file.php (error.php)