Add Application Setting to configure Container Registry token expire delay (default 5min)

This adds an option to configure Container Registry token expire delay. The default is set to 5mins (something that is also used by Docker Hub).

What is left:
* [x] Write test to check the expire_delay

Fixes: https://gitlab.com/gitlab-org/gitlab-ce/issues/17890

@stanhu I think that this should land in patch release of 8.8.

See merge request !4364

Merge branch 'make-container-registry-authentication-service-compatible-with-older-docker' into 'master'

Make authentication service for Container Registry to be compatible with < Docker 1.11

This removes the usage of `offline_token` which is only present when using `Docker 1.11.x` instead we relay on `scope`. This should make it compatible with any client starting from 1.6 (I did test only 1.8 and up).

Right now we return 403 if unauthorized user doesn't have access to anything. In all other cases we return token, but with empty `access`, which simply disallow requested action.

See merge request !4363

Fix import URL migration error

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/17956

See merge request !4321

Fix 404 page when viewing TODOs that contain milestones or labels in different projects

A user viewing the TODOs page will see a 404 if there are mentioned milestones or labels in multiple different projects. This is likely a caching bug and only occurs
when Markdown rendering occurs across multiple projects, which is why it's so tricky to reproduce. This is what I think is happening:
    
1. LabelReferenceFilter#references_in encounters label ~X for ProjectA and finds the label in the DB as id = 1.
2. LabelReferenceFilter.references_in yields [1, 'X', nil, ...]
3. Since project_ref is nil, AbstractReferenceFilter#project_from_ref_cache caches nil => ProjectA.
4. LabelReferenceFilter#references_in encounters label ~Y for ProjectB and finds the label in the DB as id = 2.
5. LabelReferenceFilter.references_in yields [2, 'Y', nil, ...]
6. AbstractReferenceFilter#project_from_ref_cache lookups nil and returns ProjectA. It was supposed to be ProjectB.
7. A is the wrong project, so the label lookup fails.
   
This MR expands the `project_ref` to the right value as soon as we have it to avoid this caching bug.
    
Closes #17898


See merge request !4312

Fix gitlab importer issue

Fixed credentials not being called correctly - probably some bad refactoring or search & replace... 

Fixes https://gitlab.com/gitlab-org/gitlab-ee/issues/565

See merge request !4301

Improve design of Pipeline view

## What does this MR do?

Improves current design of Pipelines view when there is multiple stages.
This makes the statuses clickable and makes the view more compact.

## Screenshots (if relevant)

![Screen_Shot_2016-05-21_at_01.20.40](/uploads/dd031b7af7005c7a61f3165fefa8b7c9/Screen_Shot_2016-05-21_at_01.20.40.png)

cc @DouweM @markpundsack @rspeicher @marin 

See merge request !4230

[ci skip]

Fix concurrent request when updating build log in browser

If you have a slow internet connection the trace will not be updated correctly. We need to check if our request is the latest one.

Fixes: https://gitlab.com/gitlab-org/gitlab-ce/issues/17535

See merge request !4183

Fix Error 500 in CI charts by gracefully handling commits with no durations

## What does this MR do?

In the CI charts, this MR reports the duration of a commit to 0 if it is `nil`.

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

Should we omit this commit from the chart or set it to some other value?

## Why was this MR needed?

We were getting an Error 500 here: https://gitlab.com/gitlab-org/gitlab-ce/graphs/master/ci

## What are the relevant issue numbers?

#17730 


See merge request !4245

Fix Error 500 when accessing application settings due to nil disabled OAuth sign-in sources

## What does this MR do?

When upgrading to GitLab 8.8, an admin would encounter an Error 500 due to a `nil` `disabled_oauth_sign_in_sources`. This MR ensures that the value will be a blank array if empty.

Closes #17564

See merge request !4242

Allow anonymous user to access pipelines

## What does this MR do?

It fixes an issue where the Pipelines is shown for the Anonymous users,
but they get 404 when clicked. Their session is then logged out.

Fixes #17717.

See merge request !4233

Allow anonymous user to access pipelines

## What does this MR do?

It fixes an issue where the Pipelines is shown for the Anonymous users,
but they get 404 when clicked. Their session is then logged out.

Fixes #17717.

See merge request !4233

[ci skip]

Fix MySQL compatibility in zero downtime migration helpers

## What does this MR do?

This MR fixes MySQL for zero downtime migration helpers introduced in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3860

Closes #17711

See merge request !4239

Fix the CI login to Container Registry (the gitlab-ci-token user)

## What does this MR do?

This fixes `docker login` not succeeding when trying to do CI login: `gitlab-ci-token with $CI_BUILD_TOKEN`.

cc @marin

See merge request !4236

Fix docker registry integration

See merge request !4229

[ci skip]

# Conflicts:
#	app/services/system_note_service.rb

Fix Error 500 when attempting to retrieve project license when HEAD points to non-existent ref

Closes #17537

See merge request !4151

Let users set notification levels in projects which they are not members

Fixes #9013 

See merge request !3986

Implement special GitLab markdown reference for milestones

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/3453 by @eReGeBe, with two additions:

- Move changelog item to 8.8
- Fix cross-project milestone ref with invalid project, like https://gitlab.com/gitlab-org/gitlab-ce/commit/f7348cd348ad8f4a18d74dd668283a4e236f5790 did for labels

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/13829

See merge request !3897

Allows MR authors to have the source branch removed when merging the MR


closes #13191 

The location of the checkbox might not be optimal so any feedback is welcome. Any other feedback too obviously.

Screenshot:
![Screenshot_2016-02-17_21.25.24](/uploads/a9c3eaafb39c6f5b4f0949a2278af6da/Screenshot_2016-02-17_21.25.24.png)

See merge request !2801