So it's more accessible for views to access the names of jobs.
Only filter Build#name from where we really need to download it.

It doesn't make too much sense having this standalone

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5142#note_13058785

And note that job/build_name could contain `/`

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5142#note_13047190

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5142#note_13047184

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5142#note_13047163

Basically:

    GET /api/projects/:id/artifacts/:ref_name/:build_name

Also added tests for it.

It turns out they are different:

    builds.success.latest.first

and

    builds.latest.success.first

If we put success first, that latest would also filter via success,
and which is what we want here.

* upstream/master: (117 commits)
  spec and fix for sanitize method
  remove fix validatable import url migration
  Fix typo in spec
  Update Gemfile.lock after versions were added in !5078
  Add more comments to regex
  Add changelog item
  Add blockquote fence syntax to Markdown
  Fix typo and explain the precedence of STDERR and STDOUT
  Add changelog entry for !4399
  Add reminder to not paste private SSH keys
  Make subnavigation a bit darker color
  Update ui_guide.md with button capitalize rule
  Re-use queries in reference parsers
  Use btn-danger for delete button.
  Update New Snippet buttons.
  Run bundle install.
  Add min attribute to project_limit field on user's form
  Wrong gitlab-shell version
  API: Expose shared projects in a group
  Memoize MR merged/closed events retrieval
  ...

So we redirect from ref and build_name to the particular build, namely:

* /u/r/artifacts/ref/build_name/* -> /u/r/builds/:build_id/artifacts/*

For:

* download
* browse
* file

Fix typo in factory for projects.rb

## What does this MR do?

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

## Why was this MR needed?

## What are the relevant issue numbers?

## Screenshots (if relevant)

## 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 !5100