Fixes active items being selectable

Enabled eslint

Toggle button text fix

Closes #343

Fix typo

See merge request !955

Change docs title to represent the edition

See merge request !961

[EE] Group members in project members view

See merge request !958

[ci skip] Update upgrade guide from GitLab CE to GitLab EE for 8.15

Following the steps from https://gitlab.com/gitlab-org/release-tools/blob/master/doc/release-candidates.md#creating-rc1.

See merge request !959

When the project has invitees, no group members were
returned due to a `user_id NOT IN (42, NULL)` query which
always returned [] since a `user_id` would be NULL, thus the condition
could never match.
Signed-off-by: Rémy Coutable <remy@rymai.me>

Closes #24122

Fix css lint

I merged [CE->EE](https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/953) with [failing css lint](https://gitlab.com/gitlab-org/gitlab-ee/builds/7216539), this is a fix.
It was caused by https://gitlab.com/gitlab-org/gitlab-ee/commit/d6d22a5dbd2ee04b59b2a80b3b6228575c3ea3ec on CE side.

@iamphill Please take a look if fixes are OK. If no, please send a separate MR to fix it.

See merge request !956

[ci skip]
Signed-off-by: Rémy Coutable <remy@rymai.me>

CE upstream

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)

	both modified:   .gitlab-ci.yml
	deleted by them: app/assets/stylesheets/pages/admin.scss
	both modified:   app/assets/stylesheets/pages/issuable.scss
	both modified:   app/controllers/projects/issues_controller.rb
	both modified:   app/helpers/projects_helper.rb
	both modified:   config/routes/group.rb
	both modified:   doc/api/merge_requests.md
	both modified:   lib/api/users.rb
	both modified:   spec/controllers/projects/issues_controller_spec.rb
	both modified:   spec/finders/merge_requests_finder_spec.rb
	both modified:   spec/services/projects/create_service_spec.rb
	both modified:   spec/services/system_note_service_spec.rb

CE commits: https://gitlab.com/gitlab-org/gitlab-ce/compare/14046b9c734e5e6506d63276f39f3f9d770c3699...50a784482e997cc039015e24b37d3f8a01a9cd3e

See merge request !953