Forbid scripting for wiki files

Wiki files (not pages - files in the repo) are just sent to the browser
with whatever content-type the mime_types gem assigns to them based on
their extension. As this is from the same domain as the GitLab
application, this is an XSS vulnerability.

Set a CSP forbidding all sources for scripting, CSS, XHR, etc. on these
files.

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/17298.

See merge request !1969

Remove 'unscoped' from project builds selection

This is a fix for this security bug: https://gitlab.com/gitlab-org/gitlab-ce/issues/18188

/cc @kamil @grzegorz @stanhu

See merge request !1968

[ci skip]

Prevent privilege escalation via notes API

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/15577

See merge request !1964

Prevent information disclosure via new merge request page

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/15591.

See merge request !1963
Signed-off-by: Rémy Coutable <remy@rymai.me>

Fix vulnerability that leaks private labels and milestones

This fixes vulnerability that leaks information about private labels and milestones because of  insecure direct object reference in issueable create service.
This affects merge requests and issues.

See https://gitlab.com/gitlab-org/gitlab-ce/issues/15439

This MR introduces additional check that rejects labels and milestone that does not belong to the same project issue/merg request does.

`IssuableBaseService` may benefit from encapsulating filters in separate class/module, which then may improve coherency in this class.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/15439

See merge request !1954
Signed-off-by: Rémy Coutable <remy@rymai.me>

Prevent information disclosure via snippet API

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/15580

See merge request !1958
Signed-off-by: Rémy Coutable <remy@rymai.me>

Prevent users from deleting Webhooks via API they do not own

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/15576

See merge request !1959
Signed-off-by: Rémy Coutable <remy@rymai.me>

Prevent XSS via custom issue tracker URL

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/15437

See merge request !1955
Signed-off-by: Rémy Coutable <remy@rymai.me>

Prevent privilege escalation via "impersonate" feature

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/15548

See merge request !1956

Fixes window.opener bug

Adds `noreferrer` value to rel attribute for external links

REF: https://gitlab.com/gitlab-org/gitlab-ce/issues/15331

See merge request !1953

See https://dev.gitlab.org/gitlab/gitlabhq/merge_requests/1948

Fix 2FA authentication spoofing
Signed-off-by: Rémy Coutable <remy@rymai.me>

[ci skip]

Closes #13957

Bump Git version requirement to 2.7.4 (for 8.3)

[ci skip]

See merge request !3284

Fixes routing errors for /api/v3/projects/

[ci skip]

[ci skip]

[ci skip]

Fix project destroy callback

See gitlab-org/gitlab-ee!107.

See merge request !2307

Use gitlab-workhorse 0.5.3

See merge request !2367

Generate builds when creating tag using web interface

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/4296

See merge request !2366

Optimize LDAP and add a search timeout

Related to #4282 

This merge request arranges some things in `access.rb` to facilitate some optimizations in EE (to come later). It also adds a 10 second timeout to all LDAP searches so the entire worker is not blocked if some query doesn't return in a reasonable amount of time. This timeout is configurable per LDAP server.

See merge request !2267