Compile highlight CSS separately
Move highlight-specific mixins out of mixins.scss
Rename solarized themes to match theme name as this was a smaller
change than changing all instances to snake_case

This change adds `note` to the Rails `filter_parameters` configuration.

[Master] Redact sensitive information on gitlab-workhorse log

See merge request gitlab/gitlabhq!2584

When switching to rails 5, we added migration version to all migration
classes. This patch makes it possible to run versioned migrations
also with rails 4

With a recent change in i18n, default language is not
included in fallbacks by default. This causes that
MissingTranslationData exception is raised both in
development and production mode.

This patch sets explicitly fallbacks language to english
which assures that english is used for missing translations.

This significantly improves performance and reduces memory consumption
when parsing XML files. On a test with 124 JUnit files from a CE build,
there was about a 4x reduction in processing time.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/54068

* updates Gemfile
* uses Rails 5 unless explicitly disabled

Manually includes the xterm custom colors
on the 3 files that will need it: job log page,
job terminal page, environment terminal page

Reduces main CSS bundle

Rails does a partial match for strings in the filter_parameters
configuration, so the parameter "key" causes "key_id" to be filtered
even though it's a useful parameter for debugging internal API issues.

We now revise this filter to make any parameter ending with "key" is
filtered.

Relates to https://gitlab.com/gitlab-com/gl-infra/production/issues/463

Fixes rails 5 deprecation warnings in `config/` files

Use object.assign for default option

The previous implementation would hit the database each time
and provide a dummy response. If the database goes down, this
means all application workers would be taken out of service.
Simplify this check by using a Rails middleware that intercepts
this endpoint and returns a 200 response.

This is mainly the setup of mutations for GraphQL. Including
authorization and basic return type-structure.

This adds Keyset pagination to GraphQL lists. PoC for that is
pipelines on merge requests and projects.

When paginating a list, the base-64 encoded id of the ordering
field (in most cases the primary key) can be passed in the `before` or
`after` GraphQL argument.

* `MysqlDateTimeWithTimeZone` inherits from `ActiveRecord::Type::DateTime`
  (`MysqlDateTime` is not present in Rails 5)
* explicitly set `NULL` default value for `merge_request_diff_files`'s
  `diff` column (otherwise empty string is used in a migration) and
  empty string is not allowed for text/blob fields in Mysql
* disable NO_ZERO_DATE mode for all Mysql DB connections, otherwise
  SQL queries fail on inserting `0` value for `created_at` column

The original MR [1] fixed red specs for Rails 5.
But while the failed specs were fixed, that changes brought new failed
specs which weren't caught up in [1].

This commit just fixes the fix. :)

New errors are like these:

```
Failed to upgrade to WebSocket (REQUEST_METHOD: GET, HTTP_CONNECTION: keep-alive, HTTP_UPGRADE: )
Finished "/-/boards/1/lists"[non-WebSocket] for 127.0.0.1 at 2018-06-20 18:09:26 +0200
```

[1]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/20015

Since Rails 5.0 the new framework has been added. It's called ActionCable.
It brings WebSockets support to rails applications.
By default the mountpoint of WebSocket requests is `/cable` [1].

GitLab allows using top level names as namespaces or usernames.
For example, `gitlab.com/cable` at this moment leads to a user with the
nickname `cable`.

This commit changes ActionCable's mountpoint to a reserved top level
word `-`.
This is just a stub and should not be be used in real work.

Please set correct mountpoints for each environments when configuring
ActionCable for real using.

[1]: https://github.com/rails/rails/blob/5-0-stable/actioncable/lib/action_cable.rb#L38

It fixes Rails 5.0 deprecation flooding like:

```
DEPRECATION WARNING: Passing strings or symbols to the middleware builder is deprecated, please change
them to actual class references.  For example:

  "::Gitlab::Middleware::ReadOnly" => Gitlab::Middleware::ReadOnly

 (called from <top (required)> at /builds/gitlab-org/gitlab-ce/config/environment.rb:11)
DEPRECATION WARNING: Passing strings or symbols to the middleware builder is deprecated, please change
them to actual class references.  For example:

  "ActionDispatch::Static" => ActionDispatch::Static

 (called from <top (required)> at /builds/gitlab-org/gitlab-ce/config/environment.rb:11)
DEPRECATION WARNING: Passing strings or symbols to the middleware builder is deprecated, please change
them to actual class references.  For example:

  "Gitlab::Testing::RequestBlockerMiddleware" => Gitlab::Testing::RequestBlockerMiddleware

 (called from <top (required)> at /builds/gitlab-org/gitlab-ce/config/environment.rb:11)
DEPRECATION WARNING: Passing strings or symbols to the middleware builder is deprecated, please change
them to actual class references.  For example:

  "ActionDispatch::Static" => ActionDispatch::Static

 (called from <top (required)> at /builds/gitlab-org/gitlab-ce/config/environment.rb:11)
DEPRECATION WARNING: Passing strings or symbols to the middleware builder is deprecated, please change
them to actual class references.  For example:

  "Gitlab::Testing::RequestInspectorMiddleware" => Gitlab::Testing::RequestInspectorMiddleware

 (called from <top (required)> at /builds/gitlab-org/gitlab-ce/config/environment.rb:11)
```

Enforce UTF-8 encoding on user input in LogrageWithTimestamp formatter and filter out file content from logs

Same strategy with:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/17810

See:
https://stackoverflow.com/a/29710188/1992201

Frankly I don't really understand how this works and I don't really
care either. However I tried it and it does the job. To try this,
make sure you have pending migrations, and run the server, hit the site.
It would tell you that there's pending migrations, and then run
migrations, and then hit the site again.

Without this patch, Rails would complain that "A copy of ...",
with this patch, it works without problems.

This reverts commit ddeefbdd.

This reverts merge request !17159