* 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

* Remove unused method #set_counters_maps from api controller

* Remove unused method #set_account_counters_maps from api controller

* Remove unused method Account#followers_domains

* Remove unused User.prolific scope

* Add mastodon:users:admins task to list all admin emails

* Use interpolated query style in Account.triadic_closures

* Coverage for Account.triadic_closures

* Remote spec for non-existent entry_classes helper method

This method no longer exists, and is handled by a local variable in a partial
instead.

* Remove spec for non-existent Account#ping! method

* 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

* Consolidate webfinger string creation under Account#to_webfinger_s

* Introduce Account#local_username_and_domain for consolidation

* Clean up SQL output in Tag and Account search methods

* Add basic coverage for Tag.search_for

* Add coverage for Account.search_for

* Add coverage for Account.advanced_search_for

Checking reblog vs original status was happening in multiple places
across the app. For views, this logic was encapsulated in a helper
method named `proper_status` but in the other layers of the app, the
logic was duplicated.

Because the logic is used at all layers of the app, we extracted it into
a `Status#proper` method on the model and changed all uses of the logic
to use this method. There is now a single source of truth for this
condition.

We added test coverage to untested methods that got refactored.

Fix anchor tags in some wikipedia URLs being matches as a hashtag

as well as formatting of content

and atom feed generation to some extent, as well as the way mentions are
stored