Resolve "Display "folders" for environments"

## What does this MR do?
Adds the ability to show the grouped environments inside "folders".
Adds several reusable vue components in order to accomplish the recursive tree data structure presented.

For the individual components, Jasmine tests were added.
For the ones that depend of an API response, rspec tests are used.


## Screenshots (if relevant)
![Screen_Shot_2016-11-16_at_02.00.13](/uploads/1278012c8639b999b53f080728d283e1/Screen_Shot_2016-11-16_at_02.00.13.png)
![Screen_Shot_2016-11-16_at_02.00.25](/uploads/a3d65416ddb553e1b8f0f4c8897a75dc/Screen_Shot_2016-11-16_at_02.00.25.png)
![Screen_Shot_2016-10-17_at_16.08.50](/uploads/af63efe1d2cbd5fc069408622ef4b607/Screen_Shot_2016-10-17_at_16.08.50.png)


![environments](/uploads/b5a1801766d82ab176fc60f96b6968cb/environments.gif)
## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [x] Added for this feature/bug
  - [ ] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [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 it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?
Closes #22539

See merge request !7015

Improves documentation

Adds tests

Fix prop validation for objects

Finish tests for environment item

Adds tests for toggle folder function

Environment tests

Adds tests

Adds tests.
Changes instance into a constructor

Adds tests for environments component

Adds tests assertations

Adds external URL test

Adds tests for Rollback component

Adds tests for stop component

Adds tests for actions component
Fix environment item

Init environment item tests

Move comments to the correct location

Remove array extension usage

Move build options to fixture to match view