Move global ci entries handling from legacy to new config

## What does this MR do?

This MR moves responsibility of handling global CI config entries (like `image`, `services`), from legacy `GitlabCiYamlProcessor` to new CI Config

## Why was this MR needed?

This is the next iteration of CI configuration refactoring

## What are the relevant issue numbers?

#15060

## Does this MR meet the acceptance criteria?

- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)

See merge request !4820

Assert against `ActionMailer::Base.deliveries` relatively

- Closes #19496 
- Fixes `master` build


See merge request !5082

- Look for a `change` in its size rather than asserting against an
  actual size.

- This previously failed because another spec had an email in
  `ActionMailer::Base.deliveries`, which failed this `be_nil` assertion.

Add troubleshooting section for SMTP settings



See merge request !5046

Added user avatar to header

## What does this MR do?

Adds  the users avatar to the header with a dropdown for profile & sign out.

## What are the relevant issue numbers?

Closes #18543 

## Screenshots (if relevant)

![Screen_Shot_2016-06-27_at_12.47.34](/uploads/852d0eb7075eefcf21f5cf5ff71a389a/Screen_Shot_2016-06-27_at_12.47.34.png)

![Screen_Shot_2016-06-27_at_12.47.36](/uploads/6cb29843d3a12bbf2d3ed2a7c9bde770/Screen_Shot_2016-06-27_at_12.47.36.png)

See merge request !4939

Handle custom Git hook result in GitLab UI

## What does this MR do?

This MR fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/19190
It allows to show messages from git custom hooks

## Screenshots (if relevant)

![joxi_screenshot_1467651998090](/uploads/7f814523c96712c07b4f4b52c843aab3/joxi_screenshot_1467651998090.png)

See merge request !5073

Fix dead links in the docs (Jun 2016)

## What does this MR do?

Fix dead links in the docs found as of Jun 2016.

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

n/a

## Why was this MR needed?

This MR must improve UX on docs.gitlab.com.

## What are the relevant issue numbers?

Closes #19156 

## Does this MR meet the acceptance criteria?

- No [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) updated
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !4921

Upgrade rspec-rails from 3.4.2 to 3.5.0.

Also upgrade its dependencies. Includes Rails 5 support. Working toward #14286 

Changelogs: http://rspec.info/blog/2016/07/rspec-3-5-has-been-released/

See merge request !5051

Update README.md - SSH password can be changed with `ssh-keygen -p`

SSH password can be changed with `ssh-keygen -p`

See merge request !4152

Save artifacts sizes

## What does this MR do?

Introduce ci_builds.artifacts_size as an integer, so that it's easier to access than reading from the file again.

## What are the relevant issue numbers?

Closes #18869

See merge request !4964

Feedback:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4964/diffs#note_12867416

Guidelines:
https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/testing.md#general-guidelines

> Use `context` to test branching logic.

Feedback from:
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/4964#note_12867273

Update spring to 1.7.2 to fix hanging rails console

## What does this MR do?
Update spring to 1.7.2.

## Why was this MR needed?
This fixes hanging rails console issue.

## Related
Fixes https://gitlab.com/gitlab-org/gitlab-development-kit/issues/127

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

See merge request !5066

More descriptive message for git hooks and file locks

## What does this MR do?
Most of the benefits will be in GitLab EE because we have git hooks there (push rules) and file lock features.
Instead of showing "Git operation was rejected by #{hook_name} hook" the actual problem description will be shown.
Also you will see a clear message when you edit locked file.

## Why was this MR needed?

Because we don't want to confuse our users

## What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ee/issues/713


See merge request !5067