Sync develop with stable

Closes #1262, #1267, #1293, #1303, #1287, #1291, #1382, #1438, #1129, #1109, and #1606

See merge request pleroma/pleroma!2278

Release/2.0.0

See merge request pleroma/pleroma!2273

moderation log: fix improperly migrated data

See merge request pleroma/pleroma!2277

Some of the actions used to have a user map as a subject, which was then
changed to an array of user maps. However instead of migrating old data
there was just a hack to transform it every time, moreover this hack
didn't include all possible actions, which resulted in crashes. This
commit fixes the crashes by introducing a proper database migration for old data.

Closes #1606

Wait in mix task while pleroma is rebooted

See merge request pleroma/pleroma!2225

Remove EmojiPacks from AdminFE build

See merge request pleroma/pleroma!2275

Revert "Merge branch 'update/admin-fe-without-emojipack' into 'develop'"

See merge request pleroma/pleroma!2276

This reverts merge request !2274

Once more, with feeling

Remove emoji support from AdminFE

See merge request pleroma/pleroma!2274

MastodonController: Return 404 errors correctly.

See merge request pleroma/pleroma!2270

Generate instance stats on startup

Closes #1598

See merge request pleroma/pleroma!2271

Exclude reblogs from `GET /api/pleroma/admin/statuses` by default

Closes #1596

See merge request pleroma/pleroma!2267

Do not fail when user has no email

See merge request pleroma/pleroma!2249

Update Copyrights

See merge request pleroma/pleroma!2269

Prepared statements settings

See merge request pleroma/pleroma!2238

fix for :fetch_initial_posts

See merge request pleroma/pleroma!2266

A warning was added, but their were some newlines and whitespaces missing which broke the rendering of the setting. I've added them now

ActivityPub actions & side-effects in transaction

Closes #1482

See merge request pleroma/pleroma!2089

Bump copyright

See merge request pleroma/pleroma!2265

Done via the following command:
git diff fcd5dd25 --stat --name-only | xargs sed -i '/Pleroma Authors/c# Copyright © 2017-2020 Pleroma Authors <https:\/\/pleroma.social\/>'

Done via the following command:
git diff 1e6c102b --stat --name-only | cat - | xargs sed -i 's/2017-2018 Pleroma Authors/2017-2019 Pleroma Authors/'

DOCS Add warning for fetch_initial_posts + more explicit distinction between OTP and from source

See merge request pleroma/pleroma!2262

Add warning to the fetch_initial_posts setting. Now we sometimes have people who enable this without realising the consequences (tons of posts being fetcht as each fetch makes Pleroma discover new users)
I also made a more explicit distinction between OTP and from source installs in the general explanation