* Introduce domains method to Account relation

Account had followers_domains method, which was excessively specific.
Let relation of Account have domains method instead.

* Move follow_mapping in Account to AccountInteractions

* Introduce shared examples for AccountAvatar inclusion

* Cover Account more

This commit fixes a regression in commit
f554807563.

* Add buttons to block and unblock domain

* Relationship API now returns "domain_blocking" status for accounts,
rename "block entire domain" to "hide entire domain", fix unblocking domain,
do not block notifications from domain-blocked-but-followed people, do
not send Salmons to domain blocked users

* Add test

* Personal domain blocks shouldn't affect Salmon after all, since in this
direction of communication the control is very thin when it comes to
public stuff. Best stay consistent and not affect federation in this way

* Ignore followers and follow request from domain blocked folks,
ensure account domain blocks are not created for empty domain,
and avoid duplicates in validation

* Purge followers when blocking domain (without soft-blocks, since they
are useless here)

* Add tests, fix local timeline being empty when having any domain blocks

* Add <ostatus:conversation /> tag to Atom input/output

Only uses ref attribute (not href) because href would be
the alternate link that's always included also.

Creates new conversation for every non-reply status. Carries
over conversation for every reply. Keeps remote URIs verbatim,
generates local URIs on the fly like the rest of them.

* Conversation muting - prevents notifications that reference a conversation
(including replies, favourites, reblogs) from being created. API endpoints
/api/v1/statuses/:id/mute and /api/v1/statuses/:id/unmute

Currently no way to tell when a status/conversation is muted, so the web UI
only has a "disable notifications" button, doesn't work as a toggle

* Display "Dismiss notifications" on all statuses in notifications column, not just own

* Add "muted" as a boolean attribute on statuses JSON

For now always false on contained reblogs, since it's only relevant for
statuses returned from the notifications endpoint, which are not nested

Remove "Disable notifications" from detailed status view, since it's
only relevant in the notifications column

* Up max class length

* Remove pending test for conversation mute

* Add tests, clean up

* Rename to "mute conversation" and "unmute conversation"

* Raise validation error when trying to mute/unmute status without conversation

* Adding account domain blocks that filter notifications and public timelines

* Add tests for domain blocks in notifications, public timelines
Filter reblogs of blocked domains from home

* Add API for listing and creating account domain blocks

* API for creating/deleting domain blocks, tests for Status#ancestors
and Status#descendants, filter domain blocks from them

* Filter domains in streaming API

* Update account_domain_block_spec.rb