[WIP] #17337 create login system

Todo:
* [ ] add the ‘auth’ package to the package list in the config file:  /app/config/config.php
* [ ] create a controller: users and view: login, logout, register 
* [ ] create a models user with data: username, password, group, email, last_login, login_hash, profile_fields
* [ ] check to table's name in: /fuel/packages/auth/config/simpleauth.php
* [ ] edit the template page for the entire site
* [ ] create the registration form using the model and passing it with the controller
* [ ] attach fields to this form and send it back to the controller
* [ ] change action_register function within the users controller
* [ ] add a validate function to create rule and check error for registration page
* [ ] change action_login function within the users controller