[mod:php] Modify Admin, Staff and Student Models for Authentication with password hasing

Modify the Admin, Staff and Student models by adding beforeSave() to
the model and adding PasswordHasing using md5 hash algorithm.
[mod:StudentsController.php] Modify controller for student registration

Modify StudentsController by altering the register() to add data to
Students and Users tables.
[mod:php] Implement Authentication for the project

Add Authentication for the students and place holder for Admins and Staff
Add new login.ctp view and move the content of Pages/home.ctp to login.ctp
Modify the AppController to add the AuthComponent and in the UsersController
add the login() function.