Handle can_delete and can_edit properly

This pull request introduces some significant changes:

- `render_form` macro takes `admin_view` as an argument and shows/hides save and delete buttons depending on `admin_view.can_edit` and `admin_view.can_delete` values
- in the list view, delete option is not available in the actions dropdown if `admin_view.can_delete` is set to `True`
- Lots of commented out code has been removed (no point to keep it in the files, if it can be found in the repo's history) and indentation has been fixed in few places (still a lot to do, though).

Let me know what you think. Thanks!