Documentation of omniauth-ldap limitations

Further documentation about limitations directly impacting settings of
users' LDAP servers.

Closes #2613

See merge request !1421

Improve repo cleanup task

I accidentally wrote a new script, not seeing we already had one.
But the old one did not do enough (it only handled global namespace orhpans) so I figured I should just drop in the new script.

See merge request !1298

page-title-fix

Fixed .page-title margin

See merge request !1458

Move CI variables page to project settings
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Part of #2594 

See merge request !1457

Remove 'kerberos' from auth_helper.rb for gitlab-CE.

There is no Kerberos auth in gitlab-ce, so it shouldn't be noted
as a form-driven auth mechanism in app/helpers/auth_helper.rb.
This breaks using Kerberos as a custom omniauth provider.
See issue #2510 (https://gitlab.com/gitlab-org/gitlab-ce/issues/2510).

@DouweM suggested I send in this merge request.

See merge request !1430

note about EE git hooks

Because of https://gitlab.com/gitlab-com/www-gitlab-com/issues/415#note_2131220

See merge request !1934

[ci skip]

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

Update Source Sans Pro font: adds support for cyrillic characters
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Fixes #2764

See merge request !1454

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

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

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

Add user preference to view project activity and starred project activity as default dashboard

Screenshot:

![image](https://gitlab.com/gitlab-org/gitlab-ce/uploads/5e39fa66da50e01dd9ed1c8a9ce01ea9/image.png)

Closes #2662

See merge request !1446

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

Fix grammar in admin area labels when no labels exist

Fixed grammar on Using Docker Build doc.



See merge request !1448

updating admin area > "Labels" text to "There are no labels yet.", per Stan Hus suggestion.