Remove notification settings in batches

## What does this MR do?

This improves the performance of the migration `db/migrate/20160603180330_remove_duplicated_notification_settings.rb` by removing duplicate rows in batches instead of using a single big `DELETE FROM` query.

## Why was this MR needed?

The original migration would locally take 45 minutes to complete, possibly up to hours on GitLab.com and similar setups.

## What are the relevant issue numbers?

#18289

See merge request !4529

Added 8.9 install/update guides

See merge request !4507

[ci skip]

Workhorse to serve raw diffs

Fixes (partially) #13999

Dependent on: gitlab-org/gitlab-workhorse!45

See merge request !4130

Rename ci_commit in application code

This is third iteration of renaming `[ci_]commit(s)` in application code to `pipeline(s)`.


See merge request !4464

Rename Ci::Commit in specs

This is second iteration of renaming Ci::Commit occurences, this time I try to rename all `let's` and `factories` to match what type of object is created:

1. Rename factories: `ci_[...]_commit_[...]` to `ci_[...]_pipeline_[...]`,
2. Rename all `let's(:[ci_]commit)` to `let(:pipeline)`,
3. Rename all occurrences of `[ci_]commit` to `pipeline` if Pipeline object is created

cc @grzesiek @DouweM 

See merge request !4463

License finder gem

Every time a gem is added to the Gemfile, or a gem is updated with a new dependency or change of license, LicenseFinder will check to ensure that the license in use has been whitelisted for use in the project. GPLv2 and GPLv3 libraries are not allowed to be linked-to from non-GPL projects (e.g. the MIT-licensed GitLab CE or proprietary EE), otherwise we're violating the license.

https://github.com/pivotal/LicenseFinder

See also: gitlab-com/operations#164

See merge request !3775

Fix missed colorize methods.

Fix #18250.

cc: @twk3 

See merge request !4495

Bump rouge to 1.11.0

See: https://github.com/jneen/rouge/blob/master/CHANGELOG.md

See merge request !4491

Use better_errors editor links in sherlock

Closes #18254. Uses the same editor configuration of `better_errors`
so that you don't have to configure things twice. Remember to have a
custom initializer that specifies your editor.

Example for atom. File `config/initializers/better_errors.rb`:
````ruby
if defined?(BetterErrors)
  BetterErrors.editor = "atm://open?url=file://%{file}&line=%{line}"
end
````

See merge request !4497

Remember to configure your `better_errors` editor to point to your program of preference

Add padding to bottom of wiki page, fix #12921.

## What does this MR do?
Adds padding to the bottom of the wiki page so it's not right up against the edge of the browser window.

## What are the relevant issue numbers?
#12921

## Screenshots (if relevant)

Before:

![Screen_Shot_2016-06-06_at_12.21.22_PM](/uploads/9710682a57f5e521253f17a65f896f4d/Screen_Shot_2016-06-06_at_12.21.22_PM.png)

After:

![Screen_Shot_2016-06-06_at_12.20.50_PM](/uploads/002068b072050e0f8146757a0386d30f/Screen_Shot_2016-06-06_at_12.20.50_PM.png)

cc: @jschatz1 

See merge request !4490

Make sure to mention the GNU Project and OSI-provided information regarding the GPL so no one tries to disagree with that decision.

Add gems and licenses that were previously missing. Approve a number of licenses after a bunch of research today.

Also add License Finder to CI (only runs on master).

In order to rehost all our gems in our own gem host, we need to have the legal rights to do so for every gem should they be taken down from RubyGems. License Finder automates checking of gems to ensure that we're in the clear legally.

Approved the MIT License because it essentially allows us to do "whatever" with those gems.

I am not a lawyer.

https://github.com/pivotal/LicenseFinder

Remove duplicated notification settings and add unique index

See merge request !4472

Fixed issue with activity links not being consistent

## What does this MR do?

Previously, links for opening an issue/merge request & commenting where different. Opening would only have a link on the number whereas commenting would have link on the text as well. This standardises it to include the type as well (ie. issue)

## What are the relevant issue numbers?

Closes #17621 

## Screenshots (if relevant)

![Screen_Shot_2016-06-01_at_12.12.09](/uploads/c778b007e6b6c068fcae30e34409ce98/Screen_Shot_2016-06-01_at_12.12.09.png)

See merge request !4400

Shows the edit comment button on mobile

## What does this MR do?

Shows the edit comment button on mobile.

## What are the relevant issue numbers?

Closes #17214 

## Screenshots (if relevant)

![Screen_Shot_2016-06-01_at_12.33.13](/uploads/d46b800c175a53821ea8e8af49c07641/Screen_Shot_2016-06-01_at_12.33.13.png)

See merge request !4402

Remove prev/next buttons on issues and merge requests

## What does this MR do?

Remove prev/next buttons on issues and merge requests sidebar

## Are there points in the code the reviewer needs to double check?

No

## Why was this MR needed?

The buttons were rarely used and added at least 1 query each on every page load which we could live without.

## What are the relevant issue numbers?

#18026

## Screenshots (if relevant)

Below is how it looks. Not sure if it's too much empty space. #17697 discusses a possible substitute for what to put there.

![Captura_de_pantalla_2016-06-06_a_las_11.09.26_a.m.](/uploads/7b379327aa6c608775f99bf47a9c3352/Captura_de_pantalla_2016-06-06_a_las_11.09.26_a.m..png)

![Captura_de_pantalla_2016-06-06_a_las_11.09.38_a.m.](/uploads/68bcae6754ed5ac48f1a6925fdd17d3f/Captura_de_pantalla_2016-06-06_a_las_11.09.38_a.m..png)

See merge request !4442

Add confidential issue notice in comment box.

## What does this MR do?

Adds a warning about confidential issues to the comment field when the issue is confidential.

## Are there points in the code the reviewer needs to double check?

I don't think so.

## Why was this MR needed?

It wasn't clear to users that they were commenting on a confidential issue, this makes it more explicit.

## What are the relevant issue numbers?

Fixes #15288 

## Screenshots (if relevant)

This is what it looks like at various screen sizes:

![Screen_Shot_2016-06-03_at_2.56.54_PM](/uploads/eb7f318bc19101f8514d7a4f10a77d73/Screen_Shot_2016-06-03_at_2.56.54_PM.png)

![Screen_Shot_2016-06-03_at_2.58.51_PM](/uploads/13674c3f1227b0d566b1d2aafc6712ed/Screen_Shot_2016-06-03_at_2.58.51_PM.png)

![Screen_Shot_2016-06-03_at_2.58.37_PM](/uploads/14ad419ed3ed86b7fbc080152e4030fa/Screen_Shot_2016-06-03_at_2.58.37_PM.png)

cc: @jschatz1 @dzaporozhets 

See merge request !4473