Add support for generate scaffold password:digest

* adds password_digest attribute to the migration
* adds has_secure_password to the model
* adds password and password_confirmation password_fields to _form.html
* omits password entirely from index.html and show.html
* adds password and password_confirmation to the controller
* adds unencrypted password and password_confirmation to the controller test
* adds encrypted password_digest to the fixture
Merge pull request #9699 from rubys/scaffold_password_digest

Add support for generate scaffold password:digest

* adds password_digest attribute to the migration
* adds has_secure_password to the model
* adds password and password_confirmation password_fields to _form.html
* omits password from index.html and show.html
* adds password and password_confirmation to the controller
* adds unencrypted password and password_confirmation to the controller test
* adds encrypted password_digest to the fixture