Rename methods in the LoginHelpers module
Rename methods in the LoginHelpers module

- [x] Rename `login_as` to `gitlab_sign_in`
- [x] Rename `login_with` to `gitlab_sign_in_with`
- [x] Rename `login_via` to `gitlab_sign_in_via`
- [x] Rename `logout` to `gitlab_sign_out`
- [x] Rename `logout_direct` to `gitlab_sign_out_direct`
- [x] Make `gitlab_login_with` (née `login_with`) private
- [x] Make `mock_auth_hash` private

t-zuehlsdorff/gitlabhq,dreampet/gitlab,iiet/iiet-git,t-zuehlsdorff/gitlabhq,dplarson/gitlabhq,iiet/iiet-git,dplarson/gitlabhq,jirutka/gitlabhq,dreampet/gitlab,mmkassem/gitlabhq,stoplightio/gitlabhq,iiet/iiet-git,mmkassem/gitlabhq,t-zuehlsdorff/gitlabhq,mmkassem/gitlabhq,mmkassem/gitlabhq,t-zuehlsdorff/gitlabhq,dplarson/gitlabhq,dreampet/gitlab,iiet/iiet-git,axilleas/gitlabhq,dplarson/gitlabhq,jirutka/gitlabhq,axilleas/gitlabhq,jirutka/gitlabhq,axilleas/gitlabhq,dreampet/gitlab,jirutka/gitlabhq,stoplightio/gitlabhq,stoplightio/gitlabhq,axilleas/gitlabhq,stoplightio/gitlabhq