Support commenting on a diff in side-by-side view

### What does this MR do?

This MR adds support for commenting on a diff in side-by-side (aka parallel) view. It also fixes a JavaScript bug (see !779) when the comment button is clicked on a line that already has a comment.

There is an existing bug where the comment count is not updated when a new comment is added. I'll send a MR for that later.

### Why was this MR needed?

Commenting only worked in "inline" mode. Often the side-by-side view is more conducive to writing comments.

### What are the relevant issue numbers?

Closes https://github.com/gitlabhq/gitlabhq/issues/9283

### Screenshot

![image](https://gitlab.com/stanhu/gitlab-ce/uploads/3d0a3213fde38844a681a826da18139b/image.png)

See merge request !810

Closes https://github.com/gitlabhq/gitlabhq/issues/9283

If kerberos is enabled require it

Since 'group: :kerberos' got [included in the Gemfile ](https://gitlab.com/gitlab-org/gitlab-ce/commit/2391a43a7073b4e723e9ca1f7ff19b30f8e51452) Kerberos no longer got [loaded when the app started](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/config/application.rb#L6)

This caused `Devise::OmniAuth::StrategyNotFound` error once Kerberos is enabled, failing to start GitLab .

With this we hopefully do not need to remove group from the Gemfile.

See merge request !819

Fix layout issue in header title truncation.

@douwe Thanks for reviewing this fix for the issue mentioned in https://dev.gitlab.org/gitlab/gitlabhq/issues/2314#note_48539.

**BEFORE**

![before](https://dev.gitlab.org/gitlab/gitlabhq/uploads/4ffb35f77155a92c64cfe36c66987eb0/before.gif)

**AFTER**

![after](https://dev.gitlab.org/gitlab/gitlabhq/uploads/2bb2d0c4a93164f6d47e24cdcb9a106b/after.gif)

See merge request !1867

Fix UI issues in Applications form

@douwe Thanks for reviewing this small fix.

---

Before:

![application_form_before](https://dev.gitlab.org/gitlab/gitlabhq/uploads/11fbee17ad6a4c9456cd7d6cba5ae429/application_form_before.png)

---

After:

![application_form_after](https://dev.gitlab.org/gitlab/gitlabhq/uploads/0c64214ccda6c77095f468fcb8c748f3/application_form_after.png)

See merge request !1859

Fix hooks for web based events with external issue references

The creation of cross references for external issues (which would fail)
is now prevented. This fixes a 500 error and the execution of hooks when
creating a merge request or commenting on one.

Fixes #1650, GH-9333.

This regression might have been introduced by
8f8a8ab3. There is actually a TODO by
@rspeicher mentioning external issues which is lost (unhandled) in a
later commit.

This fix is related to !766 and !804 which fix a similar issue for hooks for
Git based events.

See merge request !794

Update release doc

See merge request !1865

Improve DB dump instructions

See merge request !1868

New syntax of .gitlab-ci.yml

See merge request !1862

Look for .gitlab-ci.yml only if checkout_sha is present

Fixes https://dev.gitlab.org/gitlab/gitlabhq/issues/2396

cc @vsizov

See merge request !818

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

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

Prepare blog post in advance

Prepare the blog posts template directly after merging the old one. This way people can add add items that should not be forgotten during the month.

See merge request !816

Fix external issue tracker hook/test for HTTPS URLs

If HTTPS was used for the 'project_url' of an external issue tracker, an
error was raised because a HTTP connection was established to the
default HTTPS port.

The code has been corrected and simplified by using HTTParty.
Additionally, the request now is made directly to the 'project_url'
instead of the extracted root path.

## The bug is reproducible on gitlab.com
1. Set up a new external issue service (I used Redmine)
2. Set the project URL to 'http://example.com/redmine/projects/x' and
  click on 'Test settings' => Ok
3. Now set the URL to 'https://example.com/redmine/projects/x' and test
  it again => 500

## What is actually happening?
Web servers behave differently when a non-SSL connection is established
to a SSL port:
- Nginx / Apache 2.4: Status code 400
- Apache 2.2: <!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">...
  (no status code line is sent)
- example.com: Empty response, no status code line

## Relevant log entries
```
2015-06-04T11:10:47.972Z 16785 TID-exfks WARN: {"retry"=>true, "queue"=>"project_web_hook", "class"=>"ProjectServiceWorker", "args"=>[...], "error_message"=>"wrong status line: \"<!DOCTYPE HTML PUBLIC \\\"-//IETF//DTD HTML 2.0//EN\\\">\"", "error_class"=>"Net::HTTPBadResponse", ...}
2015-06-04T11:10:47.972Z 16785 TID-exfks WARN: wrong status line: "<!DOCTYPE HTML PUBLIC \"-//IETF//DTD HTML 2.0//EN\">"
2015-06-04T11:10:47.972Z 16785 TID-exfks WARN: /usr/lib/ruby/2.1.0/net/http/response.rb:41:in `read_status_line'
[...]
/home/git/gitlab-7.11.4/app/models/project_services/issue_tracker_service.rb:88:in `execute'
/home/git/gitlab-7.11.4/app/workers/project_service_worker.rb:8:in `perform'
[...]
```

See merge request !767

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

Update ssl ciphers

Removing all DHE suites from Nginx template SSL ciphers.

This will deny forward secrecy for Android 2.3.7, Java 6 and OpenSSL 0.9.8. but will give A+ rating on SSL labs.

Google sites also do not have DHE suites, [source](https://community.qualys.com/blogs/securitylabs/2013/06/25/ssl-labs-deploying-forward-secrecy)

> Google's sites, for example, tend to not have any DHE suites in their configuration. [2013]

See merge request !814

Allow user to customize default Dashboard page

Renames the "Design" profile page to "Preferences" and adds a field to customize the default Dashboard page:

> ![Screen_Shot_2015-06-11_at_11.12.53_PM](https://gitlab.com/gitlab-org/gitlab-ce/uploads/b5282a3be7861d1148528c6bc9e7a0e0/Screen_Shot_2015-06-11_at_11.12.53_PM.png)

See merge request !778

Remove visibility icon from projects list on dashboard and group page

## Why?

Because

* visibility level show on project page anyway
* it does not have much value. Main purpose of project list on dashboard is navigation. Avatar + project name helps this goal. Visibility icon have no effect here
* it makes UI worse because it brings separation between project avatar and name
* without visibility icon we have more space for project name. Especially important for laptops

## Screenshot

![Screenshot_2015-06-12_18.17.20](https://gitlab.com/gitlab-org/gitlab-ce/uploads/0e572388e9a337c5a535813911d08c89/Screenshot_2015-06-12_18.17.20.png)

P.S. Merge when 7-12-stable is created

See merge request !806

Remove button to all projects on Trending Projects page.

Fixes #2001.

See merge request !1860

Fix post-receive errors on a push when an external issue tracker is configured

### What does this MR do?

This MR improves upon !766, fixing errors upon a git push that occur only when an external issue tracker (not JIRA) is used. This MR takes into account that external issue trackers, such as JIRA, may close issues. Disabling the processing of post-receive commits when an external issue tracker is configured seems like the wrong behavior.

### Why was this MR needed?

When a user adds an issue reference, the refactoring in 8f8a8ab3 and a6defd15 caused `project.get_issue` to be called, causing `ExternalIssue` to be returned when an external issue tracker was configured. This object does not have a `close` method, as needed in `CloseService`. Nor does it make sense to associate a `SystemNote` with this object.

GitLab EE uses a [special case for JIRA](https://gitlab.com/gitlab-org/gitlab-ee/blob/master/app/services/git_push_service.rb#L87). I would recommend moving this logic into `CloseService` too.

### What are the relevant issue numbers?

* Closes #1700
* Closes #1720

See merge request !804

Update Irker home page

[ci skip]

Closes #1713

See merge request !812