Signed-off-by: NRémy Coutable <remy@rymai.me>

This MR enables rendering of PlantUML diagrams in Asciidoc documents. To add a
PlantUML diagram all we need is to include a plantuml block like:

```
[plantuml, id="myDiagram", width="100px", height="100px"]
--
bob -> alice : ping
alice -> bob : pong
--
```

The plantuml block is substituted by an HTML img element with *src* pointing to
an external PlantUML server.

This MR also add a PlantUML integration section to the Administrator -> Settings
page to configure the PlantUML rendering service and to enable/disable it.

Closes: #17603

Updated Turbolinks to patched version of turbolinks-classic

See https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/2048

Signed-off-by: NRémy Coutable <remy@rymai.me>

MR https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/8158 updated
the octokit Gem but did not include all the changes for Gemfile.lock.

ChangeLog: https://github.com/octokit/octokit.rb/releases

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/26114

vmstat 2.3.0 fixes an issue with reporting the incorrect # of CPUs. This is used in the GitLab Admin Dashboard.

Includes various bug fixes, mostly for Rails 5.

Changelog: https://github.com/mperham/sidekiq/blob/fc168fe393bee3ad1fcbb52cff2d84af86c38cc4/Changes.md

https://github.com/deivid-rodriguez/pry-byebug

Includes support for Rails 5.

Changelog: https://github.com/rubysherpas/paranoia/blob/879fd18caa46af70fceca2e8f46886b3eff072ec/CHANGELOG.md#220-2016-10-21

Somehow `bundle install` with an update to Sidekiq-cron caused
rufus-scheduler to be bumped, when it doesn't appear absolutely
necessary.

Closes #25160

The "Enqueue Now" button would not work in the admin panel due to
changes in the Web extension interface.

Closes #24376

The amount of gems required is quite high compared to the usefulness
of the features.

Related to !4928, !6713
Signed-off-by: NRémy Coutable <remy@rymai.me>

Fixes gitlab-org/gitlab-ce#14329

CHANGELOG: https://github.com/jneen/rouge/blob/v2.0.7/CHANGELOG.md

We use the Redis-backed session store from `redis-store` so this is
unnecessary.

Closes gitlab-com/support-forum#1270

This update adds support for Rails 5. Also update redis-rails dependencies.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/2814

This was the only thing using the `sdoc` gem, which was blocking another
gem from updating.

ChangeLog: https://github.com/samg/diffy/blob/master/CHANGELOG

ChangeLog: https://github.com/deckar01/task_list/compare/1.0.5...1.0.6