fix title of pages with active_admin_logged_out layout (fix #3428)
use same item dsl for actions and actions with dropdown (fix #2625)
join IndexAsTable default actions
extend documentation for new index actions style
remove i18n key `active_admin.update_model`

This key is not used by active admin, see #3172
remove i18n key `active_admin.create_model`
automatically set precompile assets
don't configure authentication_method if devise isn't used (fix #3467)
make root_path options configurable
base support for custom ransackers
use ransackers as default filters
rename locale iso 'no-NB' to 'nb'

see https://en.wikipedia.org/wiki/ISO_639:nb for details
remove es.active_admin.blank_slate.entry

this don't exist in 'en' and is not used by ActiveAdmin
mv locale key fr.active_admin.access_denied

mv locale key fr.active_admin.access_denied to fr.active_admin.access_denied.message

see:
https://github.com/activeadmin/activeadmin/blob/master/lib/active_admin/error.rb#L15
add some missing devise.links locals
remove {es,es-MX}.views.pagination.*

there is the `kaminari-i18n` gem to get this locales
refactor AttributesTable#content_for
refactor AttributesTable#content_for specs
add spec for settings setter
add support for `config.setting_name?`

This adds a ActiveModel like questionmark attr checker:

  inheritable_setting :foo, true
  config.foo? # => true

  inheritable_setting :foo, false
  config.foo? # => false

  inheritable_setting :foo, ""
  config.foo? # => false

  inheritable_setting :foo, "bar"
  config.foo? # => true