* Add render_views for admin/settings spec

* Add coverage for admin/settings#update

* Add coverage for admin/settings typecasting open_registrations setting

* Simplify how admin/settings finds the value for updating

* Rely on activerecord to not update a value that hasnt changed

* Add coverage for non-existent setting

* Use a constant for boolean settings

* Add admin/instances index action

* Add link to instances admin page

* View lists instances

* Instances, grouped by domain, ordered by count

* Use Account.remote scope

* Extract method: Account.by_domain_accounts

* Simplify admin/reports controller filtering for index

* Rename parameter to resolved

* Fix issue where reports view could not access filter_link_to

* Add coverage for admin/reports controller

* DRY up resolution of related reports for target account

* Clean up admin/reports routes

* Add Report#statuses method

* DRY up current account action taken params

* Rubocop styles

* Remove unused account_params method in admin/accounts controller

* Introduce AccountFilter to find accounts

* Use AccountFilter in admin/accounts controller

* Use more restful routes admin silence and suspension area

* Add admin/silences and admin/suspensions controllers

* Add Admin::BaseController to wrap admin area

Extracts the setting of the `admin` layout and verifying that users are admins
to a common base class for the admin/ controllers.

* Add basic coverage for admin/reports and admin/settings controllers