* Add option to disable two factor auth in admin accounts panel.
Closes #2578

* Add @mjankowski's suggestions.
* Moves destroy actions behind User#disable_two_factor!
* Adds spec coverage for Admin:TwoFactorAuthenticationsController and User#disable_two_factor!

* Add render_views in more places

* Delegate methods from account to user with allow nil true, so that admin accounts show view renders when missing a user

* Use actual account instances in authorize follow controller spec

* 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