gregbell/active_admin — pull request #1609 by tracedwax (2012-08-26 17:47:45+00:00)
Title: Allow a blacklist listing filters

We want to preserve active generation of filters, while
opting out of certain filters, for example associations.

Sometimes associations can be prohibitively large, for
example when there are 100,000 users and several models
which belong_to :user. That filter would have too many
items for the list to display correctly, and was causing
serious performance issues.

Example:
````ruby

class User < ActiveRecord::Base
has_many :posts
end

class Post < ActiveRecord::Base
belongs_to :user
end

ActiveAdmin.register Post do
unfilter :user
end
````