Wrap <Avatar> in account header in a link to that account's page (fixes #245)

Set packs on 2FA-related pages.  Fixes #271.

This translation key comes in from tootsuite, but the flavours system
does not use it.

Specifically, this commit:

- changes S::TFA::{Confirmations,RecoveryCodes}Controller to derive from
  S::BaseController, because this gives us the necessary actions and
  packs
- prepends set_pack to Auth::SessionsController's action chain so that
  it takes effect in time for render :two_factor

* Add aria-autocomplete='list' in Textaria

ref: https://www.w3.org/TR/wai-aria-1.1/#aria-autocomplete

* Make detect empty string brefore assign upload description

* Change code elements in keyboard-shortcuts component to kbd

* Update Korean translation

* Translate Korean for javascript

* Add missing translations on simple_form

i18n: Update some locale files

* Add Slovak translation

* Slovak translation: i18n-normalize

prevent federation of local-only statuses

Fix admin/action_logs page

2.1.0. -> 2.1.0

Conflicts:
	db/schema.rb

Update ja.js

* i18n: (zh-CN) Change `工作人员` (staff) to `管理人员`
Suggested by @Gargron at https://github.com/tootsuite/mastodon/pull/6005#discussion_r156678109

* i18n: (zh-CN) Change `协管` to `监察员`

* i18n: (zh-CN) Fix all "Are you" questions

* i18n: (zh-CN) Various improvements

* i18n: (zh-CN) Final clean-up

* i18n: (zh-CN) Change translation for 500

* i18n: (zh-CN) Remove spaces between time distances

* i18n: (zh-CN) Improve translations

* Last minute Dutch strinfupdate

* Last minute Dutch strings update

* Fixing Weblate output errors

* Fixing Weblate output errors

* Fixing more Weblate rubish

Weblate is also changing some " to ' - I think that is not a problem

* Fixing more weblate stuff

* Fixing

* Update nl.yml

Also adjust the examples for Status.as_tag_timeline to match the
nomenclature used in .as_public_timeline (e.g. "account" -> "viewer").

This commit also:

- exposes the local-only emoji so that it can be used in examples
- allows local_only to be set explicitly, i.e. for timeline filtering
  specs

* Fix overflowing emojis on some devices

* Quit visible and add padding

* Adjust empty list timeline message (#5997)

* Adjust empty list timeline message (#5997)

* Add filters to admin UI for custom emojis (#6003) + #6004

* Update fr.yml