ES: Fix. bin/elastic_repo_indexer follows config

Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/390

See merge request !276

GitLab Geo: Wiki Synchronization

We should be able to replicate Wikis it in Geo (#76) as we do with any git project.

Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/367

# Checklist

- [x] When a wiki is updated by git on secondary node, we must enqueue and buffer this action in an specific redis queue
- [x] When a wiki is updated by web UI on secondary node, we must enqueue and buffer this action in an specific redis queue
- [x] When we pool for updated projects we must also query for updated Wikis
- [x] A secondary node must receive in a different endpoint bulk notifications of updated Wikis
- [x] When a updated wiki notification is received, it must generated async jobs for every wiki, to be updated

See merge request !267

Geo documentation

documentation for GitLab Geo (#76)

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/356

See merge request !236

Update settings and documentation for per-install LDAP sync time

The setting is now per-install, rather than per-server.

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/364

See merge request !266

Fix PATH to bin/elastic_repo_indexer

Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/389

See merge request !273

Added index on git_hooks.project_id

cc @ayufan @pcarranza 

See merge request !271

On PostgreSQL this index is created concurrently.

Fixes gitlab-org/gitlab-ce#14324

- Add FAQ about different SSH port
- Add section on using a custom name for the SSH key pair
- Change image for Geo nodes admin area
- Reorganize some sections

[ci skip]

Renamed EnqueueUpdateService to be specific for Project Updates

[ci skip]

Fire merge request webhooks when a merge request is approved

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/93

See merge request !270

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/93

CE-to-EE `master` for 8.6.0-rc1



See merge request !269

[ci skip]

Allow subscribing to labels

This implement #12743 and supersedes !2799 (thanks @timothyandrew!).

- Subscribe (and unsubscribe) for labels
- When an issue/merge request is created, notify all subscribers of all its labels
- When an issue/merge request is edited, notify all subscribers of all its newly-added labels

## Done

- [x] Verify that a user is signed in to subscribe/unsubscribe from a label.
- [x] Merge conflicts
- [x] Integration tests
- [x] `issuable.subscribed?` should check subscribers and participants
- [x] When an issuable is relabeled, notify subscribers of the *newly added* labels only
- [x] Screenshots:

### Labels page

![Screen_Shot_2016-03-07_at_19.05.44](/uploads/3e69064e9e1a06ee2e27c778776c1407/Screen_Shot_2016-03-07_at_19.05.44.png)

### HTML email

![Screen_Shot_2016-03-07_at_19.07.36](/uploads/e484e06366a738385f1f6d71b52eecf7/Screen_Shot_2016-03-07_at_19.07.36.png)

### Plain text email

![Screen_Shot_2016-03-07_at_19.07.50](/uploads/dc05f710a8f7ab5eae9f72aa2110e741/Screen_Shot_2016-03-07_at_19.07.50.png)

PS: I've set the milestone to 8.6 since it's getting late for 8.5...

See merge request !3115

Add "Enable SSL verification" option to Group's web hooks form.

Fixes #370 

See merge request !248

1. Make the "subscribed" text in Issuable sidebar reflect the labels
   subscription status

2. Current user mut be logged-in to toggle issue/MR/label subscription

[ci skip]

[ci skip]

* Make comments webhooks available for Groups.

CSS style guide

Working towards what was discussed in #13552, this adds the [SCSS Linter gem](https://github.com/brigade/scss-lint) for style guide conformity in CI.

TODO:
- [x] Agree on and write SCSS Style Guide Documentation.
- [x] Document the `scss-lint` config file.
- [x] Figure out how best to run this in CI, right now it's taking longer than I would think it should.
- [x] Use CSSComb for auto-correction (Maybe just include a CSSComb config file and have developers run the node package manually if they're interested in using it?).

My logic for not using CSSComb in the first place is that, AFAIK, we don't currently require Node/NPM, even in the dev environment. Maybe I'm wrong about that? `scss-lint` is a Ruby implementation of a similar concept, but it doesn't include autocorrect.

Is there a way we can run get GitLab CI to run `scss-lint` without having to put together the full GitLab application? Seeing as it's just static analysis, it seems like a waste of time/resources.

/cc @jschatz1 @rspeicher

See merge request !3069

Remove parentheses from if statement

Otherwise Rubocop will give a warning after we upgrade it.

As discussed in !3197.

[ci skip]

See merge request !3231

Otherwise Rubocop will give a warning.

As mentioned in !3197.