Handle duplicate appearances table creation issue with upgrade from CE to EE

Closes #391

See merge request !278

Hide builds from Project's settings when the feature is disabled (EE)

Related to https://gitlab.com/gitlab-org/gitlab-ce/issues/13944

See merge request !268

Geo: ReadOnly middleware improvements

We should handle API requests (JSON) in a different way we handle normal requests.

Current implementation always redirect to root and display error messages using `flash[:alert]`.
This MR adds `{ message: "..." }` type of response when request is under `application/json` content_type.

This is a small patch/enhancement for Geo (#76)

See merge request !274

Closes #391

Ensure GithubImport::Client does not crash when the 'verify_ssl' config is not present

This fixes gitlab-org/gitlab-ce#14343 and !260 when `verify_ssl` is not present in the GitHub omniauth
settings in `gitlab.yml`.

Settingslogic allow to access optional settings through the Hash
notation: if the key is not present, it returns nil. In the present case
this will let the Octokit::Client object use whatever default value it
wants for the ssl option.

/cc @dbalexandre 

See merge request !275

Settingslogic allow to access optional settings through the Hash
notation: if the key is not present, it returns nil. In the present case
this will let the Octokit::Client object use whatever default value it
wants for the ssl option.

Fix Elastic::Indexer spec

This break was broken by !273.

See merge request !277

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]