dalpo/rails_admin_nestable — pull request #20 by gokure (2013-07-23 12:34:45+00:00)
Title: Add options :scope for nestable_list

Hi! Because the `nestable` list is ascending sort by `position_field`, but normally it is null or the default value on database (excepts sorted via `nestable`), and `rails_admin` list is descending sort by primary key. So I have feature plan implementing scope options to help sorting them or whatever.

Example:

```ruby
# models/list.rb
class List < ActiveRecord::Base
# ...
scope :by_default, -> { List.order('id desc') }
# ...
end

# config/initializers/rails_admin.rb
RailsAdmin.config do |config|
# ...
config.model 'List' do
nestable_list({
scope: :by_default # or scope: -> { List.order('id desc') }
})
end
# ...
end
```
and on the `nestable` list page have like this SQLs:
```sql
SELECT * FROM `lists` ORDER BY position, id desc
```