Adds rel="noopener noreferrer" to all links with target="_blank"

See merge request !2071

Changed it from being json links to normal links & then doing a AJAX request to get the content.

Closes #29624

add changelog entry

Closes #29543

The page param is reset when filtering or when opening, previously it was possible to get the page param stuck on a high number making it impossible to either filter or to close & open the modal and get the issues you want to see.

Closes #29616

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/29557

When using the full font-stack some the Unicode 1.1 emojis are taken up
by fonts closer up the stack and don't represent the emoji well.

```
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto,
Oxygen-Sans, Ubuntu, Cantarell, "Helvetica Neue", sans-serif, "Apple
Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
```

 - On Windows, "Segoe UI" -> "Arial" takes over
 - On mac OS, "Helvetia" -> ".SF NS Display" takes over

mac OS 10.12.3 | Windows 10
--- | ---
![](http://i.imgur.com/JI99zoH.png) | ![](http://i.imgur.com/aek8G1X.png)

---

When using a shorter emoji font-stack, everything seems to be covered
well 🎉

```
font-family: "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
```

 - On Windows, "Segoe UI Emoji"  takes over
 - On mac OS, "Apply Color Emoji" takes over

mac OS 10.12.3 | Windows 10
--- | ---
![](http://i.imgur.com/bDwpGCw.png) | ![](http://i.imgur.com/7kUwEJQ.png)

See https://gitlab.slack.com/archives/frontend/p1489690607738864

We are safe to use `data-html` because we never actually use HTML here, only the pure markdown

Closes #29572

Previously if the project had more than 100 branches or tags it wouldnt display them even after searching.
This now correctly sends an AJAx request to the backend to search for the branches/tags

Closes #29545