Removed all the unnecessary include of `WaitForAjax` and `ApiHelpers` in the specs.
Removed unnecessary usage of `api:true`

This reverts commit cb10b725c8929b8b4460f89c9d96c773af39ba6b.

https://gitlab.com/gitlab-org/gitlab-ce/issues/23036

Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

- To hold registrations from U2F devices, and to authenticate them.
- Previously, `User#two_factor_enabled` was aliased to the
  `otp_required_for_login` column on `users`.
- This commit changes things a bit:
    - `User#two_factor_enabled` is not a method anymore
    - `User#two_factor_enabled?` checks both the
      `otp_required_for_login` column, as well as `U2fRegistration`s
    - Change all instances of `User#two_factor_enabled` to
      `User#two_factor_enabled?`
- Add the `u2f` gem, and implement registration/authentication at the
  model level.

This reverts commit 3e991230.

# Conflicts:
#	app/models/project.rb

Also removes the note from the development/testing.md guide

When an admin changes a user's password for them, force the user to
reset the password after logging in by expiring the new password
immediately.

Modifies the existing "login as" feature to be called impersonation, as
well as keeping track of who is impersonating to revert back to that
user without having to log out.

Closes #2291

Signed-off-by: NJeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Signed-off-by: NJeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Remove unnecessary projects order on User#show

“Can create groups” and “Can create teams” had hardcoded defaults to
`true`. Sometimes it is desirable to prohibit these for newly created
users by default.