* Fix avatar and header issues by using custom geometry detector

Revert a part of #6508. The file passed to dynamic styles method
was not actually a file, but an instance of Paperclip::Attachment,
which broke all styles by always returning {} from the method.

One problem with GIF avatars was that Paperclip::GeometryDetector
reported wrong dimensions for them, e.g. 120x120 GIF avatar would
for some reason be detected as 120x53. By writing our own geometry
parser, we can use FastImage, which also happens to be faster than
ImageMagick, to detect image dimensions, which are also correct.

Unfortunately, this PR does not implement skipping a `convert`
entirely if the dimensions are already correct, as I found no easy
way to write that behaviour into Paperclip without rewriting the
Paperclip::Thumbnail class.

* Only invoke convert if dimension or format needs to be changed

Also don't apply "-quality 80" option which is probably the reason
for slight color differences between original and remote image
(because it would apply it twice, once on original instance, and
again on the receiving instance)

Resolve #3199

* Revert "Adjust tags and accounts page (#4534)"

This reverts commit a3e53bd442.

* Revert "feat: Cache status height to avoid expensive renders (#4439)"

This reverts commit 8eb6d171e6.

* Revert "Refactor Avatar and AvatarOverlay to have 'account' as prop instead of src and staticSrc (#4526)"

This reverts commit 5942347407.

* Revert "Update dependencies for Ruby (#4543)"

This reverts commit 22db947225.

* Revert "[Docker] Add multicore support to "make" and "bundler" (#4544)"

This reverts commit 5d408fd9aa.

* Revert "It makes no sense to try using invalid or expired link again (#4521)"

This reverts commit 47579ec58c.

* Revert "i18n: Update Polish translation (#4545)"

This reverts commit 3363a05539.

* Revert "Set false to animated options for thumbnail processor (#4547)"

This reverts commit 87f10d476c.

Resolve #3199

Fix the aspect ratio of animated GIF whose background is transparent.

* 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

Fix #2221 - Catch OpenSSL exceptions when loading remote avatars/headers/attachments
Don't strip "rel" attribute from <a> tags when sanitizing (microformats)