manage roles: MDL-8313 Provide a basic mode for the manage roles page.

manage roles: MDL-8313 Provide a basic mode for the manage roles page.

* New basic define roles mode, with just an Allow checkbox for each capability.
* Button to toggle this form to/from advanced mode.
* Also, a separate mode for viewing a role definition, rather than just showing disabled checkboxes.
* Now duplicating a role just takes to you a pre-populated add role form, so you can double-check things before saving the new role.
* Deleting a role is now logged.
* Role reordering code cleaned up.
* You can now no longer delete the last role that has admin permissions.
* This includes a general refactor of manage.php, which eliminates manage.html, and splits of define.php.