Fixing importing doc

Fixed some details about the importing links and documents.

- Added extra info to Bitbucket importing
- Organized docs in alphabetical order
- Moved Importing link to general documentation, instead of workflow (that's where Sytse asked me to add it)

Thank you @job for merging previous changes.

See merge request !1845

No need to check if `repository_ref` is present

Removed link "importing to gitlab" because it's in "Documentation". Organized links in alphabetical order.

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

Improve GitLab UI

* move logout button to top right

![Screenshot_2015-06-08_16.56.13](https://gitlab.com/gitlab-org/gitlab-ce/uploads/7de04fab52ad6b742dbea100674f9671/Screenshot_2015-06-08_16.56.13.png)

* remove issue/mr title truncation on index pages. For smaller screens it allow to read complete title of issue

![Screenshot_2015-06-08_16.57.55](https://gitlab.com/gitlab-org/gitlab-ce/uploads/9dcaadfba14f8561c12fcd29a2e70112/Screenshot_2015-06-08_16.57.55.png)

* Improve mobile UI for several pages

See merge request !783

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

There is no need to check if `repository_ref` is present as:
```
      @repository_ref = if repository_ref.present?
                          repository_ref
                        else
                          nil
                        end
```

is as same as doing:

```
@repository_ref = repository_ref
```

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

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

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

importing documents renewed

Single commit of !1813

cc @karen

See merge request !1844

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

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

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

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

Doc: Added FreeOTP to 2FA

I have just added a note about a free alternative to Google Authenticator to the documentation of your two factor authentication.

See merge request !777

Remove line under project description

## Before

![Screenshot_2015-06-05_19.44.39](https://gitlab.com/gitlab-org/gitlab-ce/uploads/e80e03a15ff32de489e61662674f8b70/Screenshot_2015-06-05_19.44.39.png)

## After

![Screenshot_2015-06-05_19.44.19](https://gitlab.com/gitlab-org/gitlab-ce/uploads/d4e2eb43802dbeee397fb6bc051b82b2/Screenshot_2015-06-05_19.44.19.png)

See merge request !776

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

Fix css alignment in header. Use scss variable
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

See merge request !775

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

Refactor web editor

* fix problem with editing non-master branch
* before commit make sure branch exists
* dont allow user change file in one branch and commit to another existing branch
* remove a lot of code duplication
* remove outdated statellite errors
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Fixes #1761

See merge request !773

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