* Do not fall back to StreamEntry if object_type is unavailable in TagManager

Since 6d6a429a, when Status, the only model
with stream_entry, and StreamEntry got its own logic in uri_for and
url_for, the purpose of the fallbacks to activity_type of StreamEntry
became unclear.

This commit removes the fallbacks. When adding another model with
stream_entry in future, consider to update uri_for and url_for.

* Cover TagManager more

ref: #3538 ("Extended information" -> "About this instance") and #3519

Signed-off-by: lindwurm <lindwurm.q@gmail.com>

* Do not default the format in ProviderDiscovery

The format should be determined when discovering, as it is in the current
implementation, and it is a flaw if it is not determined.

* Spec ProviderDiscovery

* Remove some arguments of Formatter.instance.format

* Improve spec for Formatter

* Add Japanese translations (pin)

* "ピン留め" is more general

This change follows #3519, which does the same for the Chinese variants. Or should it be simply "About"?

* Allow mounting arbitrary columns

* Refactor column headers, allow pinning/unpinning and moving columns around

* Collapse animation

* Re-introduce scroll to top

* Save column settings properly, do not display pin options in
single-column view, do not display collapse icon if there is
nothing to collapse

* Fix one instance of public timeline being closed closing the stream
Fix back buttons inconsistently sending you back to / even if history exists

* Getting started displays links to columns that are not mounted

* Remove redundant status.reply? in AtomSerializer#object

* Cover AtomSerializer more

* Add redis key "subscribed:timeline:#{account.id}" to indicate active streaming API listeners exists.

* Add endpoint for notification only stream.

* Run PushUpdateWorker only for users uses Streaming API now.

* Move close hander streamTo(Http/Ws) -> stream(Http/Ws)End (Deal with #3370)

* Add stream type for stream start log message.

* zh-cn.json: "additional info" -> "more info"

This commit changes the "extended info" (about/more) text to something that translates to "more info", as "additional info" in zh can sound like appending things to the (ugh) navbar, I guess.

Or should I just change it to "about this site" (关于本站)?

* zh-cn.json: navbar.info -> "about this site"

* zh-臺灣.json: navbar.info -> "about this site"

WarmCacheService is no longer used (removed with 5442083b ).

This fixes #2375.

Used by Intellij IDEA / WebStorm / RubyMine.

Remove protect_from_forgery in ApiController, which is disabled by the
following skip_before_action, as well.

This implementation is a bit smaller and still has the following benefits:

* No need of app/javascript/packs/custom.js
For custom stylesheet, it typically has only
"require('../styles/custom.scss')" and is redundant.

* No need to extract vendor stylesheet to another asset
Extracting vendor stylesheet could be forgotten by developers who do not
use custom stylesheet.

* Update rails to version 5.1.1

* Run `rails app:update`

* Remove the override of polymorphic activity relationship

* Silence warning about otp_secret attribute being unknown to rails

* We will only introduce form_with where we want to use remote data

Needed since merge of #3067.

- Upgrade dependencies
    - chai (3.5.0 -> 4.0.1)
    - chai-enzyme (0.6.1 -> 0.7.1)
    - sinon (2.2.0 -> 2.3.2)
- Change extensions from .jsx to .js
- Don't assign `React` to `global`
- Check code format using ESLint