Allow to disable GitLab CI

Added simple config option to disable GitLab CI

It makes all CI related requests to return 404

/cc @dzaporozhets @jacobvosmaer @vsizov

See merge request !1340

Allow custom info to be added to Help page

Fixes #2536

**Admin screen**

![image](https://gitlab.com/jeroenvanbaarsen/gitlab-ce/uploads/e62f3e0ff40558fb955f09e469293521/image.png)

**Text on the Help page**

![image](https://gitlab.com/jeroenvanbaarsen/gitlab-ce/uploads/ba315fb418e1698d8f44b88c7cc6c29a/image.png)

/cc @DouweM

See merge request !1309

Fix 500 when accessing private project when not logged in



See merge request !1336

Fix 500 on trending projects if isntance has 100k+ projects

Fixes #2576 
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !1341

Remove Cancel button from CI Project settings

Resolves https://gitlab.com/gitlab-org/gitlab-ce/issues/2568

See merge request !1337

Project header titles

Fixes my issues with !1293, see [my comment](https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/1293#note_2112289):

> No please, not this huge if/else statement again! This will get out of sync so quickly, like happened with the original page titles before the page_title helper per page :(

cc @haynes 

See merge request !1328

Fix: ci projects order

https://gitlab.com/gitlab-org/gitlab-ce/issues/2553

See merge request !1333

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

Fixes #2536
Signed-off-by: Jeroen van Baarsen <jeroenvanbaarsen@gmail.com>

Note about global keys

Because of tweet https://twitter.com/ChoboIslah/status/639565184806309888

See merge request !1931

Remove CI help

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/2556

See merge request !1325

Move partial locals out of controller

Some minor cleanup for upload/replace functionality: move controller variables into partial locals.

See merge request !1331

add repository field to issue hook data

Integrate CI navigation more tightly with project

![Screen_Shot_2015-09-17_at_09.51.56](https://gitlab.com/gitlab-org/gitlab-ce/uploads/013807ad9f89a35a4af988199c2ee92f/Screen_Shot_2015-09-17_at_09.51.56.png)
![Screen_Shot_2015-09-17_at_09.52.14](https://gitlab.com/gitlab-org/gitlab-ce/uploads/8f9bdaafeef62fa451ee3699f003cbc4/Screen_Shot_2015-09-17_at_09.52.14.png)
![Screen_Shot_2015-09-17_at_09.52.07](https://gitlab.com/gitlab-org/gitlab-ce/uploads/cb726bf0651ddb74c10fd7bae9a333fb/Screen_Shot_2015-09-17_at_09.52.07.png)

/cc @dzaporozhets

See merge request !1324

The controller_path includes namespaces, where controller_name only includes the class name without controller

Fix schema downgrade introduced by: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/1299

Fixes: https://dev.gitlab.org/ci/projects/1/refs/master/commits/2e9a7032cec02588484eb162717298d311770c7d
Introduced by: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/1299

See merge request !1326

Remove CI cronjob during migration

See merge request !1329

Create a "destroyed Milestone" event and keep Milestone events around in the DB for posterity

Also fix issue where destroying a Milestone would cause odd, transient messages like "created milestone" or "imported milestone".

Now if a milestone is destroyed, at least it will indicate in the activity feed even if it's not clear which milestone was destroyed:

![image](https://gitlab.com/gitlab-org/gitlab-ce/uploads/c89cc8a0a9fa549deac433f17b890913/image.png)

Closes #2382

See merge request !1227

Enable SSL by default

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/1135

See merge request !1299

Fix 500 on CI project settings

Fix: https://gitlab.com/gitlab-org/gitlab-ce/issues/2546

/cc @dzaporozhets

See merge request !1321

Fix displaying public projects

Fixes https://gitlab.com/gitlab-org/gitlab-ce/issues/2552

See merge request !1318