* 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 basic coverage for settings/exports controller
* Remove unused @account variable from settings/exports controller
* Add coverage for download export actions
* Remove deprecated `render :text` in favor of `send_data` for csv downloads
* Add model to handle exports
* Use Export class in settings/exports controller
* Simplify settings/exports controller methods
* Move settings/export to more restful routes
* When avatar/header are GIF, generate static versions.
Account API returns "avatar"/"avatar_static", "header"/"header_static"
Static version is the same as original for other cases
Web UI de-animates avatars in toots, lists of users
Fix#441, fix#596, prerequisite for #1064
* Fix JS test
* Add rake task to generate static avatars/headers from GIF ones, add test