* Fix #1870 - Strip control characters out of strings in AtomSerializer

* Adjust according to comment by @alpaca-tc

* Add language detection via WhatLanguage and (de)serialization of it through Atom

* Fix default language in ProcessFeedService

* Re-add newline before 'react-rails' Gem to fix groupings

Fixes Code Climate issue

* Basic onboarding modal that's shown to users once

* Lay out pages 2 through 5, add images, style modals (#1509)

* Lay out pages 2 through 5

Added images and laid out pages 2 through 5 in the jsx file. SCSS will
come, still working on just seeing if this works at all.

* Fix jsx errors, add images to modal pages, style modal pages

* Add animations to onboarding pager changes, improve wording and styling

* Finishing touches on the onboarding

* Add missing propTypes

* Update wording

* update Dockerfile: latest nodejs LTS

* also update imagemagick

* Rename admin.domain_block to admin.domain_blocks in prep for i18n improvement

* Use implicit controller/action path for i18n in admin/domain_blocks

* Add DomainBlock#accounts has_many

* Avoid i18n health warning for `en` locale by using symbol scope with :count

* Remove unused i18n key: plaintext_secret_html

* Remove unused i18n key two_factor_auth.warning

* Remove final will_paginate i18n keys

* Remove unused key two_factor_auth.recovery_codes

* Remove unused key: admin.reports.comment.none

* Remove unused reports. i18n namespace (moved to admin.reports)

* Ignore keys from locales which override activemodel and activerecord errors

* Revert "Remove unused key: admin.reports.comment.none"

This reverts commit 350ef2685fadc069e619bb6d1066190de195d942.

* Update i18n key reference to match moved location

* Add missing `en` keys to i18n

* Tell i18n-tasks to ignore missing attributes that dont need overwriting

* Add i18n-tasks unused to travis

The <link rel="mentioned" /> tag refers to accounts by href. So we were
matching the DB by the url attribute, and falling back to HTTP look-up.
However, GS and Mastodon use profile URLs as URIs, too, and the match
for that was missing. This could potentially alleviate some extra network
requests

* Adds note for instance admins.

* Addresses feedback from #1925.

* Use local vars in accounts/header partial

* Use local variable in 2fa recovery codes partial

* fix regex filter

* fixed br to linebreak and, stlip tags.

* change to send raw content

* changed to unescape in reducer

```
*An* `ActiveRecord::StatementInvalid` *occurred while* `POST </settings/import>` *was processed by* `imports#create`
Exception
----------------
PG::NotNullViolation: ERROR:  null value in column "type" violates not-null constraint
```

And `i18n-tasks add-missing -l ja` changes some quotes.

* Improve PT locale on simple_form

* Add missing keys to PT locale

* Fix yaml parse issue in ja.yml locale

* Fix issue in locales/ja.jsx

assets:precompile was failling because of this missing comma.

* Add missing french translation.

Causing this error:
[React Intl] Missing message: "navigation_bar.mutes" for locale: "fr",

* Update fr.jsx

* [Update ja.jsx] Add Muted, Video_error and sorted

* [Update ja] Added Recovery code's translation

* [Update ja] Added Two-fact/Recovery's translation

* Update ja.jsx

* Unite all mandatory rake tasks in mastodon:daily
Add mastodon:media:remove_remote task
Make mastodon:maintenance:add_static_avatars more resilient to exceptions

* Fix typo in task description

Create MediaAttachment but without actual file download when domain is blocked with reject_media set to true
Clean up old media files when creating a new domain block with reject_media set to true
Return remote_url in media attachments API if local file is not present
Undo domain block action in admin UI
Ability to enable reject_media from admin UI