QA Selectors for Batch Comment E2E Automation

See merge request gitlab-org/gitlab-ce!22681

Create users via the API

See merge request gitlab-org/gitlab-ce!22779

Allows users to be fetched/created via the API.

Don't log fabricate args

See merge request gitlab-org/gitlab-ce!22753

Prevents logging of sensitive data

Top level clusters controller

See merge request gitlab-org/gitlab-ce!22438

Use ClustersController as base while having Projects::ClustersController
to inform what `clusterable` is. Thanks @ayufan for the great suggestion
!

- View changes to work with new approach

- Fix javascript for new approach

- Fix feature specs for new approach

- Fix QA

In preparation so that we can create both cluster attached to project
and cluster attached to group.

- Move ClustersController to top level

- Move Clusters::ApplicationsController to top-level too

- Creates a Clusters::BaseController to share common functions

- Do not rely on @project ivar. Anything could set the ivar.

- Fix Vue page components due to new data-page value

Because of the controller change we have gone from
`projects:clusters:new` to `clusters:new`, so we need to update the file
location of the page components. There is somewhere a function that will
convert data-page to a file location.

On that note, projects/clusters/gcp/new/, translate to
Projects::Clusters::Gcp#new doesn't exist so replace that with
clusters/create_gcp/ and clusters/create_user/